question about Rasa 8

[Victorw]

Hello everyone!

New to this forum and need some of your advice. 

I just bought a Rasa 8 from greenteo, ~$1500. First question, has anyone bought astroimaging equipment from them before? 

https://www.greentoe.com/product/Celestron_Celestron_RASA_8_8-Inch_Rowe-Ackermann_Schmidt_Astrograph_91073?direct_shop=a062R000025IvxaQAC&utm_source=google&utm_medium=x&utm_campaign=20694721608&utm_term=&utm_content=&gad_source=1&gclid=Cj0KCQiA3uGqBhDdARIsAFeJ5r3KtCqywaQJPSKH4zWlKbd7FlZfeogL2ajSUlilaR704dQlzAmdF5MaArb_EALw_wcB 

[Victorw]

I new to astrophotography but I have been using Nikon for ~20 years with numerous cemaras and leans from 14mm to 600mm. I bought lenses from greentoe before and they seems to be ok. But not sure with something like Rasa 8.  I would also need get a mount and a cemera. Would really appreciate it if I can get some advice on these items. 

[Victorw]

And I am in Arizona so the sky is mostly clear. Thank you very much in advance for your help!

[ollypenrice]

I love the RASA 8 but it isn't perfect. I'd still refuse to swap it for anything else.

Firstly you need to match a camera to it.  A DSLR is too big to fit in front of the corrector without obscuring it. We use a ZWO ASI 2600MC Pro, which has a fairly large chip. We don't get perfect stars to the edge but can 'fix' them in post processing. A smaller chip would reduce this problem at a cost in terms of field of view.

Our image scale is about 1.8 arcseconds per pixel, which is not very demanding in terms of mount/autoguiding tracking accuracy. You need an RMS of about half that, so 0.9" RMS. When our more upmarket Avalon Linear packed up recently I chucked a very old EQ6 under it and and, quite honestly, there is no loss of quality.

You might also want to check out the issue of tilt...

Olly

[Victorw]

Thank you very much for the information! I will check out the camera and mount you mentioned. Will definitely looking into the tilt issue as well. 

Another naive question: I know Rasa is for deep sky, but can it still produce good images for jupiter-like planets? Maybe not enough focus lengh? 

[Elp]

Have you actually paid for it?

I'd be a bit cautious at the moment as last year most retailers stopped selling the 8 inch due to a manufacturing quality concern and stock was returned to Celestron I believe. It doesn't affect all scopes but I'd be dubious of any available on the market at the moment, as good as the scope is.

[Victorw]

4 minutes ago, Elp said:

Have you actually paid for it?

I'd be a bit cautious at the moment as last year most retailers stopped selling the 8 inch due to a manufacturing quality concern and stock was returned to Celestron I believe. It doesn't affect all scopes but I'd be dubious of any available on the market at the moment, as good as the scope is.

Not yet - Greentoe says order was planced ( offer accepted) - but they have not charged the card yet. Thanks for this important information. It is indeed a bit suspicious, thus I am asking around here. I bought a couple of time from Greentoe before but usualy buyers need to send individual offers. I was a bit surprised to see $1535 price pop up just in the google search. 

[Elp]

Personally I'd err caution and only buy one from a retailer with a good returns policy or from an individual whom can prove it's imaging condition. It's a scope I'd like but I've been put off because of this issue, and I can't mount a larger one which are unaffected as far as I'm aware.

[Elp]

The current option I'd look at is an Edge HD 8, with a Hyperstar you can do F2 widefield imaging, and still use it for planets at its native focal length, and use it for visual. More cost though for additional items. Currently I use a C6 like this, the edge HDs are better designed.

Edited November 18, 2023 by Elp

[ollypenrice]

18 minutes ago, Elp said:

The current option I'd look at is an Edge HD 8, with a Hyperstar you can do F2 widefield imaging, and still use it for planets at its native focal length, and use it for visual. More cost though for additional items. Currently I use a C6 like this, the edge HDs are better designed.

Each to their own, but I wouldn't touch a Hyperstar with a ten foot pole. If you read enough owner accounts, and look at their results, a pattern emerges: a few people get decent results, most don't. I agree absolutely with your earlier point, though, that a RASA should be bought only from a very reputable dealer with good returns policy.

49 minutes ago, Victorw said:

 

Another naive question: I know Rasa is for deep sky, but can it still produce good images for jupiter-like planets? Maybe not enough focus lengh? 

Nothing like enough FL. The RASA is a widefield instrument, pure and simple.

Olly

[Victorw]

29 minutes ago, Elp said:

Personally I'd err caution and only buy one from a retailer with a good returns policy or from an individual whom can prove it's imaging condition. It's a scope I'd like but I've been put off because of this issue, and I can't mount a larger one which are unaffected as far as I'm aware.

Thanks for reminding. It should be from an authorized dealer with 30 days return policy. I will double check. 

[Victorw]

6 minutes ago, ollypenrice said:

Each to their own, but I wouldn't touch a Hyperstar with a ten foot pole. If you read enough owner accounts, and look at their results, a pattern emerges: a few people get decent results, most don't. I agree absolutely with your earlier point, though, that a RASA should be bought only from a very reputable dealer with good returns policy.

Nothing like enough FL. The RASA is a widefield instrument, pure and simple.

Olly

That is a bummer... I was hoping this can image Saturn.... 

Maybe I should start with a C8 first? I actually ordered a C8 from Amazon when it was on sale a few days ago ( ~$1150). Many people said Rasa is much better, and I do like the fact that Rasa is a F2 - but if it can not image something like saturn maybe I will get start with the C8 first. 

[AKB]

1 hour ago, ollypenrice said:

When our more upmarket Avalon Linear packed up recently

No!!  Temporary, or permanent?  I still love my M-Uno, and had been using it whilst my Mesu was in disrepair (servo controller, not mechanics.)

Tony

[Elp]

They're two different animals. RASA is a widefield (shortish focal length depending on model) fast imaging scope for deep sky, things like SCTs are for planets (I've imaged Jupiter and Saturn with a short FL 360mm refractor). Fast optics are suited to reveal the depths of the skies in shorter imaging time, if you've got the hours and weather permitting you don't necessarily need fast optics. 

[tomato]

Here is a link to a thread where I attempted to image a medium sized galaxy with a RASA8 and a small pixel CMOS camera, and compared the results with a 1050mm FL 6” APO. The RASA came second.

 

[Victorw]

10 hours ago, tomato said:

Here is a link to a thread where I attempted to image a medium sized galaxy with a RASA8 and a small pixel CMOS camera, and compared the results with a 1050mm FL 6” APO. The RASA came second.

 

wow, very impressive!

[Victorw]

10 hours ago, Elp said:

They're two different animals. RASA is a widefield (shortish focal length depending on model) fast imaging scope for deep sky, things like SCTs are for planets (I've imaged Jupiter and Saturn with a short FL 360mm refractor). Fast optics are suited to reveal the depths of the skies in shorter imaging time, if you've got the hours and weather permitting you don't necessarily need fast optics. 

Looks C8 is an easier option for me now - kids can directly start looking into it. Thanks again for all the information. 

[ollypenrice]

16 hours ago, AKB said:

No!!  Temporary, or permanent?  I still love my M-Uno, and had been using it whilst my Mesu was in disrepair (servo controller, not mechanics.)

Tony

Don't know yet, Tony. I'm trying to find a manual for dismantling it. It won't be much - just a broken wire or something. It's not the motherboard for which I have a spare.

Olly