Help! UV/IR cut filter as ERF for Quark

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Rybak
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Help! UV/IR cut filter as ERF for Quark

Post by Rybak » Tue Jun 30, 2015 7:45 am

Hi all,

Would you be so kind and give me advice.

I ordered at OPTCORP chromosphere Quark for my SW 120 ED and DayStar 2” UV/IR filter for Quark as ERF (according to DayStar recommendation). Today I received such a message from OPT:

We do not have a lead time for the filter as of yet. I would like to suggest another option for the filter. Item OFU-IR-2 - http://www.optcorp.com/catalogsearch/re ... e&dir=desc - for $39.00. This is basically the same filter (more than likely made by the same manufacturer).

What do you think about this suggestion? Is it a correct replacement? Or I can purchase used Baader 2” UV/IR filter here in Moscow for about $95.00.

Thank you.
Last edited by Rybak on Wed Jul 01, 2015 10:32 am, edited 2 times in total.
Aleksey

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Lunt LS100THa, Coronado SolarMax II 90 Filter + BF 15 on WO Megrez 90, PST + SW 1025 mod, Quark + SW150/750 in test mode

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Re: UV/IR cut filter as ERF for Quark

Post by axlefoley » Tue Jun 30, 2015 8:17 am

Aleksey personally I would get the Baader, but I know nothing about the other filter.

Looks like there is one here in Australia but a bit more dollars.

Oh that's Australian dollars to.

http://www.extravision.com.au/catalog/p ... 798a830e11

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Re: Help! UV/IR cut filter as ERF for Quark

Post by grimble_cornet » Thu Jul 02, 2015 8:12 am

Hi Aleksey,
I use the 2" Baader filter you mention with my Equinox 120 and with several other scopes including a Tal 100 and an Equinox 80. It works very well allowing me to produce images like this:
Equinox120 Quark-4 Grasshopper3  2014 0911 1119 ut colour.jpg
Equinox120 Quark-4 Grasshopper3  2014 0911 1058 ut coloured_filtered.jpg
Based on advice given by Daystar, I think the 120mm scope is 'on the limit' for the 2” UV/IR cut filter as an ERF and don't allow it to track the sun for long periods of time. I have recently bought a 152/900mm scope for use with the Quark and have ordered a full aperture Baader ERF to use with it - very expensive but very safe.

As you have a Lunt 100, you may be interested to try the Quark as a double stack unit. I remove the diagonal from the LS100 and fit the Quark via a normal 2" diagonal plus the 2" Baader uv/ir cut filter. It increased the exposure from about 3 to about 18ms with my Grasshopper camera and only really works well in good seeing conditions but.......... it does work very well:
LS100 Quark Grasshopper 2015 0406 1114 ut coloured.jpg
LS100 Quark Grasshopper 2015 0406 1114 ut inverted coloured.jpg
Hope this helps.
.

.



.


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Re: Help! UV/IR cut filter as ERF for Quark

Post by Rybak » Thu Jul 02, 2015 10:04 am

Alan, Mike, thank you!
Aleksey

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Lunt LS100THa, Coronado SolarMax II 90 Filter + BF 15 on WO Megrez 90, PST + SW 1025 mod, Quark + SW150/750 in test mode

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Re: Help! UV/IR cut filter as ERF for Quark

Post by marktownley » Thu Jul 02, 2015 10:44 am

You could always mount the UV/IR filter on extension tubes on the nosepiece of the diagonal so that the filter itself sits higher up the tube and more of the filters aperture is used to block.
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Re: Help! UV/IR cut filter as ERF for Quark

Post by jetstream » Fri Jul 03, 2015 3:54 pm

I use Beloptiks UV/IR filter on my 120ED/ prism diag for the mini ERF. I heard Daystars UV/IR is from Astronomik and the Baader is said to work very well, more reflective than mine I think ( not positive).
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Re: Help! UV/IR cut filter as ERF for Quark

Post by Rybak » Sat Jul 04, 2015 1:54 am

Thanks to all.
Aleksey

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Re: Help! UV/IR cut filter as ERF for Quark

Post by Astrograph » Mon Jul 06, 2015 8:32 am

Hi

Adding to this a little late. As a dealer we offer UV/IR cuts etc as ERF's but have discovered a lot of variation. We started using Baader's 2" UV/IR but no longer do. This is because while using a Baader 2" UV/IR on the front of a 2" Diagonal (on a 100mm scope), we added a polariser to the front of a Quark to see if we could affect contrast while rotating the Quark (and adjusting the polariser in the process). It made no difference but when the polariser was removed it had been burnt and scored in an arc as it was rotated.

When the filtered light from Baaders UV/IR is felt on the hand it is quite warm, you could say hot. We know the Baader has an IR leak but the ERF is supposed to mainly block UV. The Baader is supposed to block UV from 400nm. It clearly does not.

We then moved on to Daystars own UV/IR. This is much better. It is cooler (but not cold). It is not an Astronomik filter as far as I can tell. They do recommend Astronomik but the filter graph looks different. We now offer people Astronomik's, simply because it is easier for us to supply. Both this and the Daystar pass the Calcium band but feel cooler than the Baader. Gerd at Astronomik does not approve his filters for solar use but does say people have used them happily for years.

Using an ND0.9 before a rear mounted etalon / telecentric improves contrast, but these filters are not designed to get warm or hot. After long exposure it is possible they will crack. Therefore we now offer customers Baaders 35nm Ha filter as an ERF. This is more expensive but the light from it is cool. We have tested this with a 6" scope and ND filter for hours. It has certainly restored my faith in Baader. I understand, but cannot confirm, it has the same coating as their D-ERF.

Based on our testing, it is clear that not all UV/IR cuts are the same and that the 35nm Ha filter allows bigger scopes and use of ND filters. We have also compared internal filters to front ERF's. They offer a far superior view than normal absorption types which are usually 1/4 wave, but no improvement to the Baader D-ERF (1/10 wave).

Note that even with a bit of heat coming through the UV/IR cut, this should not be an issue for the etalon. The blocking filter is basically just a narrowband Ha filter so deals with any remaining heat. It is just a slight concern if using other filters between the ERF and the etalon.

Finally it is best to push the ERF up the tube a little if possible as Mark mentioned. Putting it at the focal point gives it a very hard time and it will be less effective.

Hope this helps

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Re: Help! UV/IR cut filter as ERF for Quark

Post by Rybak » Mon Jul 06, 2015 10:04 am

Hi Astrograph

Thank you very much for adding. This is very valuable information.
Aleksey

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Lunt LS100THa, Coronado SolarMax II 90 Filter + BF 15 on WO Megrez 90, PST + SW 1025 mod, Quark + SW150/750 in test mode

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Re: Help! UV/IR cut filter as ERF for Quark

Post by nickatnight » Mon Jul 06, 2015 7:51 pm

Priceless info. Thank you.

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Re: Help! UV/IR cut filter as ERF for Quark

Post by marktownley » Tue Jul 07, 2015 5:55 am

Just curious here Rupert, why did you try the polariser and ND filter before the quark and not in the output from it?
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Re: Help! UV/IR cut filter as ERF for Quark

Post by Astrograph » Tue Jul 07, 2015 8:17 am

Hi Mark,

I only bother putting filters before the etalon as I am trying to influence the base of the CWL where it spreads out but is low brightness. Putting filters behind an etalon does very little I find. It makes a difference but not an improvement. All filters work better if they have less out of band information to reject (more S/N), so a better ERF and blocking filter should improve a given etalon in my view. Ideally we don't want to lose the light level of the CWL when removing the base wing shift, but using an ND kills light everywhere, so its not ideal but is worthwhile. I am hoping that when I get those ultra narrow Ha filters in we have discussed, they will reduce the base wing shift without reducing the peak intensity of the CWL much.

When you use your PST etalon behind your Quark, I think you are optimising the PST etalon by giving it a proper telecentric beam and pre-filtering. I don't know what band pass a PST etalon actually is, but I would bet its less than it offers in a PST because of the cheap optics in that scope, so it might be far less than the 0.8~1A advertised.

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