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By Viktorious
Time for yet another cry for help when it comes to choosing diagonal. I have read the many similar threads and gathered some knowledge (too many to start linking). I have come some way in my process and now that it is coming to final decisions I would like to hear from the experts. Not many of threads I have read end with the OP returning to deliver some review/verdict of his/her final decision. While I wait for response on some thread where I asked about the result, the eagerness in me forces me to write my own thread. Perhaps some of the people asking these questions before can now answer in my thread as experts!
I have the Nexstar Evolution 9.25 and am currently using the stock diagonal. My eyepieces are the Baader 8-24 mm zoom and the stock 40 mm Plössl. I would also like to upgrade EPs and there I'm looking at something better in 24 mm range, as well some nice low power for more FOV. I'm following threads about EPs and SCTs with great interest for this (on CN). Can say that I'm currently leaning towards the 1.25" 24 mm ES 68° and 2" 36 mm Hyperion aspheric (if going 2" route).
I'm thinking 2 alternatives (including a budget alternative for one of them). I'm looking at Baader mainly for ClickLock (and expect good optics):
Baader T2 Zeiss prism with a 1.25" ClickLock EP (T2 part #08) -OR- the 2" prism with 2" ClickLock (splurging that is). The budget alternative would be to get the non-Zeiss T2 prism instead for the 1.25". Worth noting that I would like to get the Celestron f/6.3 Reducer/Corrector. This would be for future purposes of delving into EAA but of course I would use it visually as well (especially if choosing the T2 route). The reasoning for my alternatives:
Go for the 2" Zeiss prism to theoretically get the best of the best in visual terms. I would make better use of the 46 mm baffle tube opening. Theoretically possible to combine with the R/C thanks to relative short light path (although not necessarily needed with 2" EPs). Downside of going to 2" accessories would be the cost, EPs, filters etc., on top of diagonal. Would not be able to spend all these costs at once. Cheaper route with T2 prism (especially the non-Zeiss), not only diagonal but also the other accessories. Cost of the R/C would be comparable to e.g. the 36 mm aspheric and give similar power and FOV with the 24 mm ES, i.e. the 24 mm would act as both. Extra plus is the ClickLock clamp for 1.25" with built in fine focusing not involving the mirror. Downside of knowing that not all light coming out of baffle tube is used. To get the wide FOV (24 mm + R/C) I'm adding glass to the optical train (theoretically not a good thing). I'm leaning towards the T2 as it would be a cheaper diagonal and for EPs I would only need the 24 mm and then the reducer instead of a 30-40 mm, so saving the expense of one EP. Then I would already have the reducer for continuing into EAA. The questions I hope the experts here can help with:
The old reducer vs 2" diagonal question. With R/C and the 24 mm I can get roughly the same mag and FOV as e.g. the 36 mm Hyperion (technically 38 mm vs 36 mm and 68° vs 72°). Also reading good things about the ES 68° and with R/C the EP should behave the same. Am I missing something here? The logics say that the I would lose some contrast with the R/C (not using full opening + adding elements), correct? Possibly flatter fields though (not important now, hopefully the EP threads might tell soon enough). The Zeiss vs non-Zeiss T2? Big differences? I have read a few posts on this so most to get some updated views here (have read that Baader has changed some things over the years). Using the R/C (f/6.3) with these prisms. I know f/7 is mentioned as "the limit" but also remember BillP's test where he was happy down to f/6 with the prisms (in 2014 at least). Perhaps most important: have I missed some other obvious alternative here? Maybe I have forgotten some question here but perhaps for the best as I assume those who have gotten this far are tired of reading now. Thanks for getting here though!
Thanks,
Viktor
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By astrorg
Hello
I have been away from this forum from possibly July - I never find a lot of time to do anything these days, same to be able to relax reading and interacting Astronomy forums.
I asked here a few ideas about making a solar scope or modifying whatever I had and I was recommended to also see Solar Chat Forums and I did.
Thanks to solarchatforums I have been able to do something decent and here is what I have done so far - very slowly!
1. I purchased a second hand PST and replaced its ITF with Maier one from the US and it finally had a clear image coming through + moved Etalon screw to third position - all the usual thing everybody does [after I researched it]!
2. used a new SCT screw-on short focuser [used once or twice on a LX200 R Classic] and using Teflon tape I screwed the PST Etalon to the focuser and purchased a 2" adaptor to fit on Etalon.
3. then used a Chinese 2" to 1.25 and modified the 2" side socket taking internal ring off and making 3x 120° threaded holes and 3x nylon thumb screws and used that as an adaptor to fit the original PST eyepiece holder - strangely enough at present this adaptor is also used as a tilter ... until I buy a proper camera tilter
4. then fit the above eyepiece holder into the SCT focuser with 2" to 1.252 adaptor in it and screwed the whole Gold PST tube with Etalon in it and made a BETTER PST - see image
5. I also initially tried a 2.2x DSLR camera Lens magnifier in front of PST and it decently works too - so PST will be fine for full solar disk mainly and without the 0.5 angstrom - not forcibly needed, I am probably around 0.7 as it is!
6. more importantly, I decided to make my own 90mm solar scope using the above bits and pieces.
7. with the help of Solar Chat Forums [great guys with a lot of knowledge, some are professional - i.e. they know the optics mathematical details - which helps] I purchased a cheap Bresser AR90/900
8. the ONLY usable thing there ... is the main tube, a nice and thick tube - the rest is ALL plastic!!!
I dismounted all parts and saw tube shorter ... a bit too much ! - I could have saved ~6cm really as I went with original ideas, but forgot I was using a different telescope from my initial thoughts - silly me!
So, I added a 6cm extension - no problems there to reach the 20cm inward needed for the PST Etalon which has ~20cm FL
9. initially I used a Tuna Fish 100g tin to adapt the SCT focuser onto my AR152 and fit Etalon inside the focuser to get near the 20cm needed- lets call it Quark unit - which it is really!
It worked well, so I decided to add a second focuser to tune the Etalon ... getting back to AR90/900 ...
10. I was trying to avoid overspending, I could not afford to spend too much - then I remembered I had a unused AR102SX which in my mind I guessed ... the focuser should over AR90/900 and it did!
It just fits perfectly - then drilled three holes for the holding screws et-voila'
11. I purchased a second hand 75mn Baader D-ERF and fit it INSIDE the AR90 tube at about 20cm inside from the front air-spaced doublet lenses, as there are the usual internal rings soldered in and just sit on it and I have about 70mm aperture - i.e 70mm width from the D-ERF for photons to get through.
At that ~20cm distance from front lenses the beam is still very large - probably about 60-65mm - there is no heat in between - no need for air-escaping holes
12. when I have the time I will make a solar finder scope and fit it on the tube - not that is really needed - I usually use CDC to get there almost over The Sun [having an almost exact spot on the yard!] - then use my eye without eyepiece and look thourgh the PST eyepiece holder for solar shinging and centre the telescope over The Sun.
Well, it works well after tuning Etalon focuser correctly and then focusing/tuning Etalon etc. - the usual.
See some images - still learning imaging/processing and a lot more to learn about Solar ... a lot!
I will probably need to get a Power-mate 2.5x when I can afford it!
1st mod - without the original black box - it works so much better - better focusing and sharper viewing too.
This is the AR90/900 shorten tube with AR102SX focuser and adaptors to test it normally
This is complete with the Quark Unit on the right side
Since this image there have been some changing - do not use the revelation adaptor any more and added a 6cm 2" extension.
Here are some images:
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By Richard Shaw
I acquired a second hand Coronado PST. The focus knob doesn't seem to have any effect on the image and, although it turns, it feels as if something inside the scope is "slipping".
Is it worth opening up and taking a look to see the focus knob in action?
Is there anywhere that services the PST without sending it outside the UK?
Are there any nasty surprises if I open it up (springs, pressure points etc)?
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By w665gc
https://www.astroshop.eu/telescopes/tecnosky-apochromatic-refractor-ap-70-478-quadruplet-flat-field-ota/p,57327
How to know this? I have read that with 65/420 scopes you cannot use 2" diagonals because there isn't enough backfocus.
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By SacRiker
I recently acquired a PST and had my first light today...it took a bit of work but I was able to see some great stuff through the EP. However, when I tried to hook up my smartphone to the scope with a phone adaptor I was completely unsuccessful in capturing any good photos. Everything looked way out of focus and I couldn't come close to seeing any of the prominences on the phone that I saw visually. Is this due to the PST's setup? Or am I doing something wrong? I was attempting to do it with an 8mm EP.
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