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Can anyone recommend an AZ Refractor?


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In theory DSO imaging on AZ mount is possible. You just need a field de-rotator. Most of the large professional observatory uses Az mount. The question is whether you are willing to pay for a accurate field de-rotator and a AZ mount that will track accurate enough for AP.

Alternatively a C6 SE can be used for AP if you are willing to pay another £800+ for a Hyperstar and focuser upgrade

http://starizona.com.../hyperstar6.htm

Also, refractors are not really that good for planets compared to SCT and Mak. For a start your refractor will need to be a Apo or a very slow achromat. The former is very expensive and the latter is huge and would negate any weight advantage of a refractor. Then there is the price, a C6 cost about the same as a good 80mm APO and less than any 4" models. A well collimated and cooled C6 will outperform most 80mm APO on planets and DSOs. Dewing is a minor issue that can be fixed with a £30 dew shield.

If you are determined to use a AZ mount for AP, a C6 SE with hyperstar is probably one of the best option.

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Thanks for the replies guys!

I am genuinely blown away by that Hyperstar! I think I've decided on the Celestron 8SE. I've put a lot of thought into it and spoken a lot with other more knowledgeable people than myself and think that overall, and in the long run, that'll be the best choice. Coupled with the idea of a Hyperstar I'm super impressed, and think that in a year or so once I've got to grips with the 8SE and finished my exams I can focus more on that 'grade' of photography.

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Thanks for the replies guys!

I am genuinely blown away by that Hyperstar! I think I've decided on the Celestron 8SE. I've put a lot of thought into it and spoken a lot with other more knowledgeable people than myself and think that overall, and in the long run, that'll be the best choice. Coupled with the idea of a Hyperstar I'm super impressed, and think that in a year or so once I've got to grips with the 8SE and finished my exams I can focus more on that 'grade' of photography.

Be careful with Hyperstar though. I heard it's not straight forward plug and play. Also a C8 is heavier than a C6 which may affect the performance of the SE mount.

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I checked the weight, seems like the 8" OTA is only a couple of pounds heavier than the 6" so I shouldn't think the mount will be hindered.

I'm looking into the Hyperstar now, seeing exactly how it works.

It works well for people who are very good technically. The most accurate appraisals may not be found on the Starizona website...

If you are not up for an EQ mount I honestly doubt that you are up for a Hyperstar. Best to say it.

Olly

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It works well for people who are very good technically. The most accurate appraisals may not be found on the Starizona website...

If you are not up for an EQ mount I honestly doubt that you are up for a Hyperstar. Best to say it.

Olly

It's not that I don't want an EQ mount, I'd love one. However, at the current time I'm looking for portability and set-up speed.

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..... I'm looking for portability and set-up speed.....

On that last point, schmidt-cassegrains do need longer to cool than some other designs. Once you have the scope at the observing site will you need to stay with it or can you leave it to cool ?

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On that last point, schmidt-cassegrains do need longer to cool than some other designs. Once you have the scope at the observing site will you need to stay with it or can you leave it to cool ?

How long is the cooling period?

I'm pretty sure I can do some less-intensive observing of say, The Moon for about half an hour whilst I wait...

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How long is the cooling period?

I'm pretty sure I can do some less-intensive observing of say, The Moon for about half an hour whilst I wait...

A C6 takes about 45 minutes, a C925 is over 1 hr if they are stored in a warm house. C8 should be somewhere in between. SCT cools downs faster than Mak, but slower than open tube designs.

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A C6 takes about 45 minutes, a C925 is over 1 hr if they are stored in a warm house. C8 should be somewhere in between. SCT cools downs faster than Mak, but slower than open tube designs.

My house is quite literally sub-zero temperatures. I have an air cooler - I'm sure it won't take much longer than 20 or so minutes if I've cooled it down significantly before hand.

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I had a nexstar5 and tried imaging with it. Yes I have seen the pics on the web and know it can be done but it's beyond my skill and I would suggest beyond most beginners abilities to get good pics out of it. If poor telescopes put people off astronomy I would suggest that poor equipment puts people off astrophotography. I have seen what people achieve with less than ideal equipment on here and people with eq3 and eq5 get better pics. I would never recommend a nexstar se for dso imaging you need to spend a lot of money on them to get half decent images. If astrophotography is a bottomless pit of expense using an se mount to get good photo's is doubly so. I admit I am not a skilled imager but my nexstar never encouraged me to learn those skills all it gave me was frustration. I love the nexstar as a compact visual scope but you would be better off with an astrotrac and long lens for imaging and just using your nexstar for visual. Just my opinion I hope I am wrong so good luck and I look forward to you rubbing my nose in it on the imaging boards

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Haha. This made me smile a little.

No offence to you, but I really do hope I can prove you wrong. If not, que sera sera. There's no harm in trying to take photos and if it doesn't bode well I'll still have a great scope that I'll enjoy using nightly! :)

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Since you are determined to image with an Alt-Az mount, instead of the single fork C8 SE, I'd suggest you pick a dual fork Celestron CPC 800 or a Meade LX200 just to up your chances of succeeding.

An Alt-az mount needs to track in three axis at variable rates while a EQ mount only needs to track in 1 axis at constant rate. As such the precision required for an Alt-Az mount is much greater than a EQ mount.

In the real world, only professionals image with Alt-Az mounted scope and they do it with professional grade equipment with a professional grade budget. Almost all amateur image with GEM mounts.

IMHO, an EQ mount is much easier to use than a Alt-Az even for visual observation, but in the end it is your money. If you think you can image with an Alt-Az mounted scope, then go ahead.

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Haha. This made me smile a little.

No offence to you, but I really do hope I can prove you wrong. If not, que sera sera. There's no harm in trying to take photos and if it doesn't bode well I'll still have a great scope that I'll enjoy using nightly! :)

I hope you prove me wrong too as I said I look forward to you rubbing my nose in it and I am being sincere not ironic very best of luck to you. I agree with keith the cpc 800 would up your chances a little
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Mine only tracks in two ...

NigelM

That's because you haven't fitted a field de-rotator (3rd axis). Objects in the sky moves in an arc, if you do long exposure on a Alt-az, the image would gradually rotate and leave star trail in the image. A field de-rotator is needed to counter this.

http://www.optcorp.com/product.aspx?pid=210-421

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Yes it's possible to capture faint deep sky objects imaging with an AltAz Mount. I've done so with my Nexstar SLT using 40 second subs... ok I needed 150 of them to get the bubble nebula (an Ha target with an unmodded dSLR), but it was there and clear. The biggest problem, it gets very, very frustrating after a relatively short period. Your sub length, imaging without a derotator, and avoiding field rotation effects, is limited by where in the sky you are imaging, and the focal length has no bearing on the time. However, if the mount drives are insufficient for the focal length and tube weight over those time frames, you can expect to lose a significant number of subs.

I was able to image M31 with 2 minute subs, but was losing 50% of them due to drive train issues, and that was using an ST80, so hardly a heavy weight or long focal length.

At the end of the day, whilst a large number of short subs will work, the results are easier and I've found, better, with a smaller number of longer subs, and you have to have some form of EQ tracking for that.

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An 8" SCT (any flavour) is great for observing and a fine choice for Lunar / planetary imaging with a webcam or high frame rate camera (DMKF/DFK) and a barlow or Powermate. You can give deep sky imaging a try but the evidence is strongly against you that it would be very good. So long as—as you say— you understand that, then it should be okay. If it turns out you don't get the results you hope for, if you bought a second hand telescope to begin with, you would stand to recoup most if not all of your investment.

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