Solar Spectrum and direct connection to a refractor

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solarGain
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Solar Spectrum and direct connection to a refractor

Post by solarGain »

Hi to you all.
I am attempting to run my Solar Spectrum ASO 0.5 ang. etalon on the back of my CR-150 telescope.
This year has been ‘dier’ (spelling) with my 200mm HaT- no images, last year some 30+ images at all resolutions. Anyway, I want to run this combo to take advantage of small refractor imaging.

I think that I am in touching distance of having it come to focus.

I have found two components that make this happen a M42 / T2 short 15mm tube screwed into the SS and a 2” short tube from a Twist-Lock Adapter by Baader. This is the shortest I can go! Baader must do a direct ‘short’ connector but I haven’t found it. Any ideas to help me out.

Oh, I have written to both SS and Baader for some ideas but they are under a lockdown!

John
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Re: Solar Spectrum and direct connection to a refractor

Post by christian viladrich »

Hello John,
Just to be sure, do you have a telecentric in your setup ?
Could you post a picture to see what it looks like ?


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

Hi John! Good to see you here, and welcome to SolarChat. Feel free to discuss whatever here, no rules like the other place.

Yes, agree with Christian, a picture of the 'rear end' will help see what is going on.

Mark


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Hi Guys, yes its been awhile.

So the images (1) are as loaded into the tail end of the CR-150 HD.
(2) Looking down the 2" short barrel.
(3) In a row, 2" short barrel, T2 15mm short item and SS ring connector.
Other than that at the other end of the SS is 0.4x Baader reducer (this all per the Hat).
AS it was I decided to set the HaT with this this morning and have 2 processed images, I had to catch the seeing by 'eye' watching the SSM so I know that this 0.4x works.
I hope that I have provide sufficient info. Any ideas will be very useful.
All the best
John
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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

!_The order of the photos are reversed!


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Re: Solar Spectrum and direct connection to a refractor

Post by christian viladrich »

So you don't use any telecentric system ?


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

Yeah, where is the telecentric?


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Ah, so given that I have a choice of two of them which is likely to give me the most use?
It so happens that Baader are offering 10% off goods purchased today!
John


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

For f8 refractor I would go with the 4x if you are using it full aperture, however, given pants seeing if you stopped down the scope to 120mm then you could use the 2.7x telecentric that comes with the HaT. I regularly use my 2.7x telecentric with my 100mm f10 and Quark.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

I'll have to read a little more about these systems to get comfortable with the investment. The 150mm, f/8 was only meant to be a backstop if the seeing was not good enough with the HaT. As it was seeing was bad yesterday having set up before 9 and my best images fell into place 2-3 hours later. So fickle the weather this last 4 months.
So I could possibly run the 2.7x stopped down to 120mm, might be best in the short term.
Another question, where can I buy 2" components, I remember that Frederick mentioned 2" comps. in a initial discussion about the introduction of the HaT. This bringing it to a maximum of 50mm focal distance in addition to the f/27,5 - (2.7x telecentric) making it I guess f35!
John


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

What bits do you need to get John? What are you trying to do?


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

The idea is can I get to ~f/35 by extending the FL of the 2.7x telecentric. They take 2" 'short' tube sections.
'


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

I have remove the 2.7x telecentric from the HaT, it took two of us. I am now unable to fit it to my 2" focuser tube there is nothing in my!


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

solarGain wrote: Sun May 10, 2020 10:15 am The idea is can I get to ~f/35 by extending the FL of the 2.7x telecentric. They take 2" 'short' tube sections.
If you're struggling at f27 I think you will really struggle at f35.


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

solarGain wrote: Sun May 10, 2020 11:54 am I have remove the 2.7x telecentric from the HaT, it took two of us. I am now unable to fit it to my 2" focuser tube there is nothing in my!
The Airylab telecentric is SCT thread. Some 2" diagonals use this, if the nosepiece and eyepiece holder from one unscrews this can go on the telecentric. Otherwise one of these https://www.firstlightoptics.com/adapte ... -back.html and one of these https://www.firstlightoptics.com/adapte ... aptor.html


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Ok, thank you very much for the lead on the components.
The f35 is for the HaT only, I've used the f27,5 a few times, I can only dream.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

I have just checked that my silver focuser tube is 55/56mm in dia. with threads. So a threaded SCT connector will not work with this focuser tube.


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Re: Solar Spectrum and direct connection to a refractor

Post by christian viladrich »

solarGain wrote: Sun May 10, 2020 7:41 am in a initial discussion about the introduction of the HaT. This bringing it to a maximum of 50mm focal distance in addition to the f/27,5 - (2.7x telecentric) making it I guess f35!
John
Hi John, I am not sure what you mean by this. In case we want to reach f35 just by adding extra spacers in the f/27 telecentric, well ... it does not work like this. You need to change the rear lens of the f-27 telecentric to have a f-35 telecentric. AiryLab offer this option.
Hope this helps.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Thank you very much for clearing this attribution up. I have been searching for the original posting but have failed to find it.
As it happens I contacted Frederic last year about the f/35 option and was told that they had all been sold.I had plans to use it in La Palma?


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Re: Solar Spectrum and direct connection to a refractor

Post by marktownley »

solarGain wrote: Tue May 12, 2020 9:01 am I had plans to use it in La Palma?
Ahh yes, had forgotten about La Palma, definitely the better place for the HaT ;)


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Re: Solar Spectrum and direct connection to a refractor

Post by Astrograph »

I don't think its been confirmed yet but for the refractor you need a telecentric to get it up to F30. Really the easiest way is to use the Baader TZ-4. You will also probably need an extension tube on the back focuser.

One other thing I don't see mentioned is an ERF on the 150.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Well I found the link to Frederic's "Setup with HaT" from March 23 2015
Screen Shot 2020-08-14 at 12.20.19.png
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Where a spacer is used to get to f/35.

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Is this plainly impossible.

I'am reading all the way thru' "Commercial Solar Filters" at present.
All the best
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Re: Solar Spectrum and direct connection to a refractor

Post by Astrograph »

You cannot use a 'spacer' to increase the focal ratio with a telecentric. The 2.7x Airylab telecentric can only be increased to 3.5x using an additional lens set which is specially made for the 2.7x.

The HaT telecentric was designed so it is just attached directly on the back of the Edge 800. With a refractor, if you position a telecentric inside the focal point you find that the new back focus position becomes that amount x the multiplier. Therefor put a 4x, 50mm inside the focal point and the new focal point becomes 200mm further back. This is why you cannot just stick a telecentric on the back of a scope and expect it to come to focus, you normally always need to use an extension. The Baader TZ's have instructions for the optimum position.

Focal ratio is focal length divided by aperture. Spacers do not change that.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Rupert Hi.
I had second thoughts about posting this, but it proves what was said "It is possible to increase the F/D by adding a spacer...""
I've given up on the idea of a f35 system many years ago, but if someone made such a system I might jump for it, but, I'm concentrating on Hires Ca-K now and SHS/ SHG imaging in time.
All the best
John


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Re: Solar Spectrum and direct connection to a refractor

Post by christian viladrich »

Hello,
I don't know whether this is relevant or not in the discussion, here are some explanations further to the ones provided by Ruppert.
Airylab provides two telecentric lenses for the Celestron SC :
- one for f/27
- one for f/35.
Both share the same front doublet, but differ from the last lens (to one toward the camera) and the spacing between the front doublet and this third lens.

So changing the f-ratio is done by changing the spacing and the third lens. Changing only the spacing would degrade the optical quality with no impact of the f-ratio.

Hope this helps.


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Re: Solar Spectrum and direct connection to a refractor

Post by solarGain »

Well, this makes more sense now, thank you for your full knowledge on this.
This helps.
All the best
John


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