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Old 22-01-2021, 09:27 PM
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lazjen (Chris)
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Refractor Scope Options

I've got a Sharpstar 107PH (FL 700mm, FR 6.54) but I am now thinking of getting something with a wider field (maybe around 400 to 500mm-ish?) and faster FR. I've tried various reducers on the Sharpstar, but I've never been really satisfied with the results.

I'd like to get a scope (refractor only) that has an imaging flat field for full frame - for the future, as I probably won't start with that at first.

What are my choices? And what other things do I need to think about? I've started googling, etc, but it's a slow process trying to work through the spec sheets looking for details. I thought I might get a bit of a list first and go from there.
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Old 22-01-2021, 10:56 PM
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Can't go past a Esprit 100. F5.5 natively with 3.5" focuser means it'll have even illumination across full frame sensors.
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Old 22-01-2021, 11:41 PM
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Have a look here, seems to fit your requirements:


https://www.teleskop-express.de/shop...ure-f-4-4.html
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Old 23-01-2021, 07:24 AM
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Originally Posted by glend View Post
Have a look here, seems to fit your requirements:


https://www.teleskop-express.de/shop...ure-f-4-4.html
That sounds impressive on paper. But I would worry that at F4.4 the importance of a quality focuser and exacting alignment of optics would not really be possible at that price point. I could be wrong. I would check out Cloudy Night Reviews first or search for images on Astrobin using it.

The Stellarvue smaller refractors have plenty of good images on Astrobin and on this site. Andy used one for quite a while.

Greg.

Last edited by gregbradley; 27-01-2021 at 11:51 AM.
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Old 23-01-2021, 07:34 AM
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I found review thread.

This is the 94EDPH F5.5 with a .8X reducer. So its the same scope.

https://www.cloudynights.com/topic/7...t-impressions/

I didn't read the whole thread but it seemed fairly positive.

Greg.
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Old 23-01-2021, 08:00 AM
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Thanks for those - I'll start looking at them. (Esprit, 94EDPH and Stellarvue)

I've also found:
* Tele Vue-NP101is f/5.4
* Takahashi FSQ-85EDX f/5.3
* Takahashi FSQ-106EDX4 f/5

Significant price range across these options.

Can't seem to find anything suitable from APM, TEC or CFF.

Edit: William Optics Gran Turismo 81 IV f/5.9 (although it's not giving me as much difference as some of the other options). I noticed the Stellarvue were in a similar situation.

Last edited by lazjen; 26-01-2021 at 01:19 PM. Reason: Spelling
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Old 23-01-2021, 09:03 AM
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Quote:
Originally Posted by that_guy View Post
Can't go past a Esprit 100. F5.5 natively with 3.5" focuser means it'll have even illumination across full frame sensors.
the espirit 100ed is hard to beat at the pricepoint. I've been looking at options for a new larger imaging scope but the espirit sits in such a sweet spot you have to go a long way from it to find something worthwhile in my opinion.
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Old 23-01-2021, 09:22 AM
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Camelopardalis (Dunk)
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Chris, fwiw my Esprit 100 is one of my favourite scopes
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Old 23-01-2021, 09:28 AM
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Have any of you used an Esprit with a full frame camera? Reading the specs suggests it doesn't support that?

Last edited by lazjen; 26-01-2021 at 01:20 PM. Reason: Spelling
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Old 23-01-2021, 09:32 AM
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Yup, a couple of years back I did some wide shots with the 6D on the back.

The imaging circle stated for the 100 is 40mm, which is pretty honest. A full frame sensor is only a touch larger.
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Old 23-01-2021, 04:53 PM
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Plenty of examples of people getting good results with full frame and espirit100ed on astrobin. Here is one but search around. http://https://www.astrobin.com/7rhlva/C/
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Old 23-01-2021, 05:53 PM
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Thanks, that is a very good example!
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Old 23-01-2021, 09:36 PM
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Don't think I can justify the price of the Tele Vue or the Tak vs the Esprit. I just can't see 2 to 3 times the cost as being worth it.

That TS-Optics 94EDPH is quite tempting, but I wish there were more images out there to review (this is pretty good though: https://www.astrobin.com/24i1mn/ - using ASI6200). It's also, by default, a wider fov than the Espirit. And would be close to $1K cheaper too, I think (even with shipping, duties, etc).

Is there a 0.8 reducer that works well with the Espirit?

Last edited by lazjen; 26-01-2021 at 01:20 PM. Reason: Spelling
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Old 23-01-2021, 09:46 PM
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Quote:
Originally Posted by lazjen View Post
Thanks for those - I'll start looking at them. (Espirit, 94EDPH and Stellarvue)

I've also found:
* Tele Vue-NP101is f/5.4
* Takahashi FSQ-85EDX f/5.3
* Takahashi FSQ-106EDX4 f/5

Significant price range across these options.

Can't seem to find anything suitable from APM, TEC or CFF.

Edit: William Optics Gran Turismo 81 IV f/5.9 (although it's not giving me as much difference as some of the other options). I noticed the Stellarvue were in a similar situation.

CFF makes a 92mm F6 and a 105 F7. The field flattener is good for a 16803 sensor (50% larger than full frame). A Riccardi reducer works with these
giving F4.5 for the 92mm scope and F5.25 for the 105 F7.
My CFF 105 F6 has a test report showing 99.4% strehl in green. That is best strehl ratio I have seen. Ex Zeiss optician. Very high end.

APM also do a 105 F6 I think unless its F6.5.
TEC smallest refractor is the 140mm. They did make a 110 F5.6 briefly. I get the idea these smaller scopes are not good money earners.

Greg.
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Old 23-01-2021, 10:16 PM
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Quote:
Originally Posted by gregbradley View Post
CFF makes a 92mm F6 and a 105 F7. The field flattener is good for a 16803 sensor (50% larger than full frame). A Riccardi reducer works with these
giving F4.5 for the 92mm scope and F5.25 for the 105 F7.
My CFF 105 F6 has a test report showing 99.4% strehl in green. That is best strehl ratio I have seen. Ex Zeiss optician. Very high end.

APM also do a 105 F6 I think unless its F6.5.
TEC smallest refractor is the 140mm. They did make a 110 F5.6 briefly. I get the idea these smaller scopes are not good money earners.

Greg.
CFF - that's superb. The 92mm would be more what I had in mind. 6 to 9 month delivery time though.

The smaller scopes probably take about the same time to make as some of their larger counterparts and provide less margin overall.
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Old 24-01-2021, 09:13 AM
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+1 for Stellarvue - My faithful high performing (3xApods) little SV70t will soon be on the market as it does not cover full frame.

However Vic re-engineered the entire line to now cover FF cameras.

The SVX objectives are completely, uniquely and individually hand-crafted and tested.
While the SV's can pass with a Strehl rating of .93-.97, the SVX's are optimized to .98 or better.

"The Bluester" here on IIS has the SVX80 and it is an absolutely superb instrument. I want one!

https://www.astrobin.com/full/sgpqgv/0/
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Old 24-01-2021, 10:48 AM
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The Finance Department has suggested that I could get a Tak if I really wanted.

As per usual though as I start researching something, I end up with more options than I expected and more questions to answer. To explain a bit further: I have my dome and my permanent mount setup. What I am working towards is getting "long term" scopes in place before I retire from work in a few years time. From there I expect to have a higher turnover on the cameras as technology progresses.

My mount (CEM120EC2) can take a lot of payload, so I'm aiming to put everything on it. Right now that's the RC10, Sharpstar 107PH, Coronado 60 (and/or SV70ED).

I'm planning on the this refractor choice to replace the Sharpstar and the SV. I am still pondering a change on the RC10 for something bigger (concern is managing the movement of the scope on/off the mount). The solar scope setup will be reviewed later.
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Old 24-01-2021, 01:58 PM
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Quote:
Originally Posted by lazjen View Post
Don't think I can justify the price of the Tele Vue or the Tak vs the Espirit. I just can't see 2 to 3 times the cost as being worth it.

That TS-Optics 94EDPH is quite tempting, but I wish there were more images out there to review (this is pretty good though: https://www.astrobin.com/24i1mn/ - using ASI6200). It's also, by default, a wider fov than the Espirit. And would be close to $1K cheaper too, I think (even with shipping, duties, etc).

Is there a 0.8 reducer that works well with the Espirit?
there is a ricardi brand that some use and I have a 0.65x starizona APEX that works with the espirit 100ed, but this is limited to APS-C sized sensors...think Ricardi likewise but googlize to confirm. I find f5.5 native quite nippy in any case so rarely use the APEX... makes focus, tilt etc exponentially more fussy...can be done, but I'd rather as easier life :-)
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Old 24-01-2021, 04:27 PM
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I am very happy with my SVX80T. I can't see that leaving my collection for a long long time.
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Old 25-01-2021, 09:48 PM
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Originally Posted by Robert_T View Post
there is a ricardi brand that some use and I have a 0.65x starizona APEX that works with the espirit 100ed, but this is limited to APS-C sized sensors...think Ricardi likewise but googlize to confirm. I find f5.5 native quite nippy in any case so rarely use the APEX... makes focus, tilt etc exponentially more fussy...can be done, but I'd rather as easier life :-)
Yes, I think that reducer is probably a big too much to deal with and I agree an easier life is preferred. Somewhere around f5 +/- 0.5 would be ok for me to deal with - I think.
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