Solarscope filters SF70

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Solarscope filters SF70

Post by Radon86 »

Hi All,

I made an enquiry about buying a SF70 h-alpha kit for my ED70 refractor. This is what I got back from the Isle of Man company.

Is there a huge jump in quality of image of a SF70 filter compared to other etalons and the Quark for example ? or is the seeing/atmosphere turbulence the main problem? Can anyone show the quality comparison between ther SF70 (? double stack is twice the cost ) ! Email reply below::

=========================================================================================
Many thanks for your email and interest in Solarscope products. The best hydrogen alpha filter to use with the Altair ED70 refractor is the SF-70 filter. I use this is combination with that telescope myself.

The Solarscope SF-70 filter’s front mounted element (in front of the telescope) contains the energy rejection filter and the etalon. The etalon does have an unobstructed 70mm clear aperture and is therefore a perfect fit for your instrument. The blocking filter unit (containing a 20mm diameter interference filter plus a number of other blocking filters fits into the back of the instrument.

The Solarscope SF-70 hydrogen alpha filter consists of the following:

1. Front mounted etalon unit
2. Blocking filter unit
3. 2” to 1.5” adaptor unit for blocking filter
4. Adaptor plate for the front mounted unit to fit on to the customer’s telescope (in your case your Altair Starwave telescope)
5.All the above packaged in a black, fitted transport case

The price of the SF-70 is £3650.00 plus VAT/ taxes (where applicable) and shipping.

The is no downpayment required with the order. When the instrument is ready to ship we will advise the customer that it is ready so that payment can be arranged. The current delivery time is 6-7 weeks.

The DSF-70 (double stacked SF-70) contains everything listed above for the SF-70 plus a second 70mm clear aperture etalon and a second blocking filter unit to ensure it can be used as a single- and double stacked instrument. The cost of the DSF-70 is £7200 plus VAT / taxes (where applicable) and shipping.

The SF-70 is designed so it can be double-stacked at a later stage if required. The double-stacking includes a second etalon and a separate, specifically adjusted blocking filter unit, so that a double-stacked instrument can be used both single-and double stacked. The cost for double-stacking an existing SF-70 instrument is £3600.00 plus VAT/ taxes (where applicable) and shipping.

Please do not hesitate to contact me if you require any further information.

Best regards

Helmut

=============================================================================================
Thanks.
Magnus


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Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
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Re: Solarscope filters SF70

Post by Montana »

Magnus, this is an image I got with a single SF70, I'd like to see a Quark beat that :) It was a real beauty. Full discs are easy, for a Quark it is not so easy.

https://www.flickr.com/photos/alexandra ... otostream/

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Re: Solarscope filters SF70

Post by Radon86 »

:hamster:
Thanks Alexandra!
My mouth is locked half open in astonishment...I am seriously thinking of buying a SF70.

Was this single stack or double stack, as double stack is twice as expensive !


Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
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Re: Solarscope filters SF70

Post by Radon86 »

HI Alexandra,

Astonishing Alexandra,
I thought you had a Solarscope 100 filter. Did you upgrade from 70 to 100 SF filter somehow ?

Thanks
Magnus


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Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
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Re: Solarscope filters SF70

Post by Radon86 »

Montana wrote: Tue Dec 14, 2021 8:29 am Magnus, this is an image I got with a single SF70, I'd like to see a Quark beat that :) It was a real beauty. Full discs are easy, for a Quark it is not so easy.

https://www.flickr.com/photos/alexandra ... otostream/

Alexandra
Hi Alexandra,

If that is a single stack SF70, then I would be content with that...a double stack can wait for another day..

Thank you.
Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
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Re: Solarscope filters SF70

Post by Montana »

This was a single stack SF70. It was Ken's personal one that he gave to me on loan while my SF100 was broken. So if it were Ken's it was probably the very best one in existence, so unknown if they are all like that, but it was better than my SF100 to be truthful. I'm still not happy with my SF100, the double stack unit is perfect and always has been, the single stack unit is like a naughty child. I'm off to the Isle of Man on holiday in June and I hope Helmut can have a look at it for me. The service from Helmut is first class. You get what you pay for :) I think Highbury Mark has a SF70 (perhaps double stack) hopefully he may chip in.

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Re: Solarscope filters SF70

Post by Radon86 »

Thanks Alexandra,
Much appreciated.

Magnus


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
Mount: SW HEQ5 Pro, SW EQ3 Pro Synscan (SW = Skywatcher),Vixen Polarie tracker (portable setup)
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Re: Solarscope filters SF70

Post by Bob Yoesle »

Hi Alexandra,
I'm still not happy with my SF100, the double stack unit is perfect and always has been, the single stack unit is like a naughty child. I'm off to the Isle of Man on holiday in June and I hope Helmut can have a look at it for me.
I hope you can get the DSF100 sorted out - they have great potential.

I did let Ken know about the IR issues with the ERF (in addition to the BF). I thought they might have addressed this - did you ever get the ERF recoated with what I think is a revised IR blocking coating? I found the combination of the OEM ERF with a Baader DERF offered optimum IR blocking (easily better than either alone) and much improved thermal stability.

Note the OEM ERF had a lot of IR transmission 700 -800 nm, and the Baader does a much better job there, whereas the OEM was much better out to 1550-2500nm:

Sol-ERF-lin.jpg
Sol-ERF-lin.jpg (110.31 KiB) Viewed 3220 times
Baader-D-ERF.jpg
Baader-D-ERF.jpg (98.1 KiB) Viewed 3220 times

The result of using the Baader DERF with the OEM SF100 ERF was far better than the OEM alone, and had the thermal stability and contrast very near the Tucson SM90 DS with the central spacer:

DERF use cmp.jpg
DERF use cmp.jpg (272.02 KiB) Viewed 3220 times
this is an image I got with a single SF70, I'd like to see a Quark beat that :)
Me too, but I'd actually IRL have to be diagonally parked in a parallel universe for that to happen...


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Re: Solarscope filters SF70

Post by Montana »

Thanks Bob, the problem is not enough heat, not too much. I can put it on the scope and it is off band and the wheel doesn't go far enough round. I can wait from 5 minutes up to an hour twiddling my fingers when suddenly, pop it goes on band and the wheel works. It needs to be on band and in range at much lower temperatures 5-20 degrees. I can't wait till 25 degree days for it to be in range of the tuning wheel :(

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Re: Solarscope filters SF70

Post by Bob Yoesle »

Hi Alexandra,

Boy does that sound familiar. When I first got the DSF100's (based on Solar Scope's "unobstructed" design, reputation of their smaller filters, and testimonials of others) I found they were completely off-band when set up, and for the life of me I thought how could they sell these things at all - let alone the prices they commanded. The SM90's were essentially on-band and easily tunable as soon as I put them on the scope.

After 10 - 20 minutes without seeing much H alpha detail (but it would vary to a degree) I would just pack up the DSF100's and think about slitting my wrists over my foolishness (I took out a home equity loan to get them!) Eventually I discovered it could take up to two hours or more for them to "warm up" and get on-band. Then I tried adding the DERF (after sorting out the BF IR leak issue with Ken), and the etalon(s) stabilized very quickly and were on-band and performed as one would expect. I let Ken know, and why I thought they had such fickle behavior.

Images in the previous post were from an apples-to-apples set-up DSF100 versus SM90/90 when using a Baader DERF110:

DSF100 v SM90DS DERF comp.jpg
DSF100 v SM90DS DERF comp.jpg (471.88 KiB) Viewed 3172 times

YMMV; but while you wait for June to roll around, you might borrow or otherwise give the Baader DERF110 a try and see what happens - hopefully someone in GB would be willing to let you borrow one. Couldn't hurt and may give Helmut a heads up in ruling things out.


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Re: Solarscope filters SF70

Post by Montana »

Bob, I do have the Baader DERF 100mm, the problem is that when I use this the etalon NEVER warms up. That is the point, they aren't over heating. They need to warm up in the Sun to get the banding within the screw reach, so putting the DERF makes them remain cold. I need the heat. It is fine when it is a hot summers day, then the ERF keeps them cool so when a passing cloud comes over they remain stable, but when the temp is cold (like most of the time) the ERF prevents the Solarscope from heating up.

I need Helmut to adjust the tuning screw so that it is on band when cold, then the DERF will really help!

Kind regards
Alexandra


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Re: Solarscope filters SF70

Post by Bob Yoesle »

Very interesting Alexandra, and perplexing!

Air-spaced etalons are considered pretty temperature stable when compared to solid gap etalons, as the air temperature and the resultant air density changes are relatively small and result in similarly small changes in etalon gap refractive index and much more stable thermal performance. I originally got the DERF for reduced IR passing through the SM90's (the the RG630 ERF has no IR blocking) and leading to thermal loading and cycling and the resultant early deterioration and failure of the blocking filter's ITF filter.

The thermal effects problem I had with the SF100 was that due to their large diameter and the lack of a central spacer caused the etalon plates (due to their small but non-zero CTE) to deform when exposed to the Sun, and the bandpass therefore changed across the etalon and the overall band-pass broadened so much that essentially it had the appearance of being off-band (Lunt uses three as opposed to Coronado using a single central spacer to mitigate this). It would take a considerable amount to time for the etalon plates to "settle down" and provide a uniform gap and good performance. Adding the DERF to the OEM ERF apparently acted similar to a central spacer in that it reduced the amount of etalon gap non-uniformity due to differential thermal effects on the etalon plates (A & B):

Etalons air spaced crp.jpg
Etalons air spaced crp.jpg (133.95 KiB) Viewed 3126 times
Adapted from Sidorin et al.


If your SF100 needs the tuning screw (tilt adjustment) to be further adjustable (more tilt), this implies the etalon has a very high CWL - which is generally not good for etalons and may introduce "banding." If you have access to a Hydrogen spectrum tube, you could judge the how high the CWL is by observing how large the central interference ring is. As seen below - the top image shows an etalon with an ideal CWL which is very near to being on-band and needs a minimal amount of tilt to be brought on-band. The lower picture shows an etalon with a very high CWL, and no amount of tilt (CWL blue-shifting) brought the etalon on-band.

Ideal v high CWL.jpg
Ideal v high CWL.jpg (630.93 KiB) Viewed 3126 times

You can also judge the etalon gap uniformity by noting how much the central diameter ring changes across the etalon diameter - the less the better. If you have an etalon with too high a CWL, you would need to have new spacers to get the CWL down to be closer to but not exactly being on-band. It may be that you are dealing with issues of thermal stability (thermally induced etalon gap differentials) and an etalon with a too high a CWL. Lastly, warmer temperatures can affect the the thickness of the etalon spacers (CTE causes these to expand - red-shift - when warmer) and adds another layer of complexity into the mix. However, this is generally minimal and requires only a slight change in tilt tuning in my experience. The DERF also mitigates this issue for temperature stability.

I hope Helmut is able to get you sorted out. This should be hopefully covered as a warranty issue even if you need new spacers, as clearly there has been something amiss since you originally got the filters.


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Re: Solarscope filters SF70

Post by Highbury Mark »

Hi Magnus - have now PMd you.
I should add that there are no temperature issues with the 70mm etalons. My DS system comes on band immediately and there’s no variation in performance through a long observing session. Keeping my fingers crossed that Alexandra’s problems can be sorted out by the factory.
I’m very happy with my filters, though the single stack on its own is not particularly impressive - on a par with the previous Lunt scopes I’ve owned. Certainly nothing like Alexandra’s borrowed SF70. So I use it all the time in DS configuration. We are very fortunate that Solarscope prices are much cheaper here in the U.K. than in many other markets, and the customer service is top notch. But there is always variability with Ha etalons, so buying new you can never be certain of filter quality until they’re pointing at the sky. Having said that, you have a better chance of a great filter with Solarscope than any other manufacturer in my view.


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Re: Solarscope filters SF70

Post by astro-piet »

I own a Solarscope SF-70 single stack since 2011, with a TeleVue 76 refractor.
Just like Mark up here, I never noticed severe temperature related issues with my SF. My SF70 IMHO certainly keeps up with the Lunts, Coronados and Quarks I occasionally looked through. Moreover, I am the only one without rusted ITF fuss so far ;).
Though, the H-alpha image in my SF set is not entirely uniform on band, certainly not visually looking at the entire solar disk at lower magnification, see this sample image of March 5th, 2021.
a-ap_SunHalfa_H-alfa_050321_114736_g3_b3_ap324.jpg
a-ap_SunHalfa_H-alfa_050321_114736_g3_b3_ap324.jpg (60.75 KiB) Viewed 2654 times
Photographically, much can be obscured by enough magnification (see image of last Friday below) and correct adjustment of the tuning screw pushing the histogram to the lower end as far as possible. Some retuning has to be done after aiming at different parts of the sun. The optimum however always stays somewhere within reach of the tuning screw so far.
ap_111643_230422_ZWO-ASI290MM_zon-halfa_L_g3_b3_ap408.jpg
ap_111643_230422_ZWO-ASI290MM_zon-halfa_L_g3_b3_ap408.jpg (526.91 KiB) Viewed 2654 times
@Bob, in my case, do you think a DERF filter might still help to improve the uniformity of the H-alpha image, or is it rather a waste of money?
BTW, @Alexandra, I strongly hope for a quick recovery of your SF!
Clear skies, Piet


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Re: Solarscope filters SF70

Post by Radon86 »

astro-piet wrote: Tue Apr 26, 2022 8:50 pm I own a Solarscope SF-70 single stack since 2011, with a TeleVue 76 refractor.
Just like Mark up here, I never noticed severe temperature related issues with my SF. My SF70 IMHO certainly keeps up with the Lunts, Coronados and Quarks I occasionally looked through. Moreover, I am the only one without rusted ITF fuss so far ;).
Though, the H-alpha image in my SF set is not entirely uniform on band, certainly not visually looking at the entire solar disk at lower magnification, see this sample image of March 5th, 2021.
a-ap_SunHalfa_H-alfa_050321_114736_g3_b3_ap324.jpg

Photographically, much can be obscured by enough magnification (see image of last Friday below) and correct adjustment of the tuning screw pushing the histogram to the lower end as far as possible. Some retuning has to be done after aiming at different parts of the sun. The optimum however always stays somewhere within reach of the tuning screw so far.
ap_111643_230422_ZWO-ASI290MM_zon-halfa_L_g3_b3_ap408.jpg

@Bob, in my case, do you think a DERF filter might still help to improve the uniformity of the H-alpha image, or is it rather a waste of money?
BTW, @Alexandra, I strongly hope for a quick recovery of your SF!
Clear skies, Piet
Hi Piet,
Thats fantastic Piet. Nice to see the SF70 filter working so well. I dont seem to come across these very often here. I will look out closely for your posts !!

Magnus


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Re: Solarscope filters SF70

Post by Highbury Mark »

astro-piet wrote: Tue Apr 26, 2022 8:50 pm I own a Solarscope SF-70 single stack since 2011, with a TeleVue 76 refractor.
Just like Mark up here, I never noticed severe temperature related issues with my SF. My SF70 IMHO certainly keeps up with the Lunts, Coronados and Quarks I occasionally looked through. Moreover, I am the only one without rusted ITF fuss so far ;).
Though, the H-alpha image in my SF set is not entirely uniform on band, certainly not visually looking at the entire solar disk at lower magnification, see this sample image of March 5th, 2021.
a-ap_SunHalfa_H-alfa_050321_114736_g3_b3_ap324.jpg

Photographically, much can be obscured by enough magnification (see image of last Friday below) and correct adjustment of the tuning screw pushing the histogram to the lower end as far as possible. Some retuning has to be done after aiming at different parts of the sun. The optimum however always stays somewhere within reach of the tuning screw so far.
ap_111643_230422_ZWO-ASI290MM_zon-halfa_L_g3_b3_ap408.jpg

@Bob, in my case, do you think a DERF filter might still help to improve the uniformity of the H-alpha image, or is it rather a waste of money?
BTW, @Alexandra, I strongly hope for a quick recovery of your SF!
Clear skies, Piet
I think it’s unlikely a D-ERF would improve the uniformity of your 70mm filter Piet, as I haven’t heard of any other Solarscope filter below the 100mm being affected by temperature. I’d be interested to hear from anyone with a different experience though.
However, when Lunt made the 75Fha external filter (now relatively rare, which is a shame because they made a great double stack package with the LS80), I think they used three spacers to maintain the uniformity of the etalon. Perhaps they thought an unobstructed 75mm filter was either too expensive or too difficult to manufacture?
Admittedly, with the double stack SF70, and both filters fully screwed in, I can’t get a perfect uniform image either. It requires careful tuning of both filters AND ‘clocking’ of both filters - ie unscrewing them by up to a full turn - to really bring them on band across the field of view. It took many months of experimentation to find the perfect positions, and even today I still move them slightly from session to session for best results. Never read about this technique in the owner manuals, but it’s essential for getting the best out of external filters in my view.


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Re: Solarscope filters SF70

Post by Radon86 »

Thanks Mark,
I had no idea there would this amount of calibration work on those SF70 front mounted filters.

Magnus


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Re: Solarscope filters SF70

Post by marktownley »

Highbury Mark wrote: Sat Apr 30, 2022 7:27 pm Admittedly, with the double stack SF70, and both filters fully screwed in, I can’t get a perfect uniform image either. It requires careful tuning of both filters AND ‘clocking’ of both filters - ie unscrewing them by up to a full turn - to really bring them on band across the field of view. It took many months of experimentation to find the perfect positions, and even today I still move them slightly from session to session for best results. Never read about this technique in the owner manuals, but it’s essential for getting the best out of external filters in my view.
Hi Mark

How are the etalons fixed to the OTA?

Mark


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Re: Solarscope filters SF70

Post by Highbury Mark »

marktownley wrote: Sun May 01, 2022 2:41 pm
Highbury Mark wrote: Sat Apr 30, 2022 7:27 pm Admittedly, with the double stack SF70, and both filters fully screwed in, I can’t get a perfect uniform image either. It requires careful tuning of both filters AND ‘clocking’ of both filters - ie unscrewing them by up to a full turn - to really bring them on band across the field of view. It took many months of experimentation to find the perfect positions, and even today I still move them slightly from session to session for best results. Never read about this technique in the owner manuals, but it’s essential for getting the best out of external filters in my view.
Hi Mark

How are the etalons fixed to the OTA?

Mark
Hi Mark - I have an adapter (made by Solarscope, silver in the attached image), which screws into the TV85 lens cell when the dew shield is fully retracted. The two solar filters then screw into the adapter.
2EE0C0A0-772E-4E3A-BFFA-A1431A4FCCD4.jpeg
2EE0C0A0-772E-4E3A-BFFA-A1431A4FCCD4.jpeg (2 MiB) Viewed 2533 times


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Re: Solarscope filters SF70

Post by Highbury Mark »

Boso36 wrote: Sun May 01, 2022 11:23 am Thanks Mark,
I had no idea there would this amount of calibration work on those SF70 front mounted filters.

Magnus
I have ‘best clocking positions’ for different eyepieces through the binoviewer. For example, If I’ve been using 32mm Plossls (48x with a 2.6x GPC), and perfected the disc for on-band uniformity, and change to 24mm Panoptics (64x) for a closer and wider view, much of the Sun suddenly looks washed out. If I then unscrew the outer filter by about 3cm, the detail and contrast reappears.


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