To change or not to change??

[Grimmeister (Anthony)]

Hi Everyone,

I am considering a change in my imaging set up and wanted to get some feedback from the people here as to what they would suggest? I know this is a bit of an open question so I would like to try and keep it within the realms of the two scopes I have listed (I am sure there are a myriad of other options but feel these best fit my budget and needs).

Ok so currently I have a GSO RC8 and while this is a good little scope I have always wanted to go bigger (hence my EQ8 purchase). To that end I am looking at either of the Bintel Newtonian or the Sky watcher Newtonian.

• Bintel (GSO) 300mm F4 Newtonian Reflector
• Sky watcher 300mm F4 Newtonian Reflector

Both scopes are similar in size and weight but differ in cost by around $600. The only real differences between the two appear to be the focuser (the Bintel model has a 3” focuser, the Sky watcher has a 2” one) and the brackets as they appear more sturdy on the Sky watcher. Lastly the Bintel scope seems to have a fan module fitted where the Sky watcher doesn’t.

To me it seems pretty clear cut but I suspect there may have been some cost cutting areas that affect the important stuff such as the optics (hence my question???).

So I am asking those that have experience with these scopes or general feedback as to what you would buy if faced with the same scenario or do you think the RC8 is just as good and I should stick with it?????

Thanks

Anthony

[Grimmeister (Anthony)]

83 views no opinions???? Might just have to try it out then

[AstroJunk (Jonathan)]

Not so much as an opinion, more of an observation.

Skywatcher are currently churning out superb mirrors...

[Peter.M]

Honestly, with the gear you have I feel the best investment into your astrophotography hobby would be a cooled mono CCD. You have a solid mount, and two good scopes. Both scopes listed will probably be ok optics wise, but mechanically will frustrate you to death. When purchasing you also need to factor in collimation tools, and I would strongly suggest an OAG and more sturdy focuser.

I know you wanted someone to tell you which one is better, optically they will both suffice, but I honestly believe that both scopes will let you down mechanically.

[Grimmeister (Anthony)]

Thanks Jonathan, good to hear so positives from the mass produced and will definitely take this into consideration, maybe this is the price difference justification between SW and GSO/Bintel.

Hi Peter, I probably should update my signature , I have a Central DS 600D cooled camera now and am very happy with it as I get limited time under the skies and don't think I would get the most of a mono camera with the time I have.

I appreciate your honesty in the mechanical side of things, if you can elaborate a bit I would be grateful. The driver for wanting bigger was that I have an RC8 at the moment and from what I read a 12" scope will be able to better resolve the finer details (something I feel lacking under the SEQ skies with a smaller scope). I would opt ofr an RC12 but cost is a bit prohibitive after the EQ8 purchase

WRT collimation tools, I have these but you are quite correct in the change over needing other items such as coma correctors and additional plates and maybe even an OAG

Having said that my first experience with that was woeful LOL so would like to steer clear of OAG's as long as possible. I have read that Newts are more prone to flexing so perhaps that would be the mechanical issues you refer to????

Again that's for the advice, it will definitely weigh in to the decision making process.

Cheers

Anthony

[Peter.M]

Originally Posted by Grimmeister

Thanks Jonathan, good to hear so positives from the mass produced and will definitely take this into consideration, maybe this is the price difference justification between SW and GSO/Bintel.

Hi Peter, I probably should update my signature , I have a Central DS 600D cooled camera now and am very happy with it as I get limited time under the skies and don't think I would get the most of a mono camera with the time I have.

I appreciate your honesty in the mechanical side of things, if you can elaborate a bit I would be grateful. The driver for wanting bigger was that I have an RC8 at the moment and from what I read a 12" scope will be able to better resolve the finer details (something I feel lacking under the SEQ skies with a smaller scope). I would opt ofr an RC12 but cost is a bit prohibitive after the EQ8 purchase

WRT collimation tools, I have these but you are quite correct in the change over needing other items such as coma correctors and additional plates and maybe even an OAG

Having said that my first experience with that was woeful LOL so would like to steer clear of OAG's as long as possible. I have read that Newts are more prone to flexing so perhaps that would be the mechanical issues you refer to????

Again that's for the advice, it will definitely weigh in to the decision making process.

Cheers

Anthony

My experience with newts is that without an OAG it is very hard to eliminate flexture for longer subs. This depends on how long you want to go of course, but currently I shoot 30 minutes narrowband with good results. My GSO newt had huge issues holding collimation as it changed orientation which I put down to the steel tube, the sub standard mirror cell, and flimsy spider system. As far as a larger scope recording more details, I would be very cautious. I'm not sure that this will be the case. As far as I am aware, more aperture will resolve stars better, but as far as detail im not so sure.

I think that the local seeing will play a greater role as well as the sampling of your setup, which may well be better for deconvolution with the RC8.

[Grimmeister (Anthony)]

Originally Posted by Peter.M

My experience with newts is that without an OAG it is very hard to eliminate flexture for longer subs. This depends on how long you want to go of course, but currently I shoot 30 minutes narrowband with good results. My GSO newt had huge issues holding collimation as it changed orientation which I put down to the steel tube, the sub standard mirror cell, and flimsy spider system. As far as a larger scope recording more details, I would be very cautious. I'm not sure that this will be the case. As far as I am aware, more aperture will resolve stars better, but as far as detail im not so sure.

I think that the local seeing will play a greater role as well as the sampling of your setup, which may well be better for deconvolution with the RC8.

Hi Peter,

Thanks again , definitely more reading on my part required and appreciate the honesty before I make any jump . I have obviously miss-understood an article I read about aperture and resolution of details. I will look into the deconvolution side of things as I am not sure what that means (still a steep learning curve to go for me).

I still like the idea of an F4 over an F8 due to the light gathering capacity but as you rightly pointed out I can go 10+ minutes subs (tested at 20 minutes as a max without issue) at the moment without any real hassle on the gear I have so introducing flexure into my system would be a step backwards.

On to some more reading

Thanks again.

Anthony

[Shiraz (Ray)]

Hi Anthony.

resolution of detail will depend only on the atmospheric seeing with an aperture of 300mm. The optics in either telescope will be quite good enough to resolve detail to better than 0.5 arc seconds, but the atmosphere will only let you image detail down to about 2 arc seconds in good conditions - so the atmosphere will always be the limiting factor.

The shorter focal lengths and larger apertures of the 300mm scopes will help with sensitivity compared to your current scope - expect about 4x the signal levels (or 1/4 the time needed).

As Peter has pointed out, mechanical stability is a problem with these scopes. If you want to use one for imaging, try to keep the weight of your imaging train to a minimum. The 600D and a necessary coma corrector should be just within the capability of the supplied focusers, but you may wish to consider something a bit stronger (eg a Moonlite). OAG is also a very good idea to overcome flexure issues.

At f4, both scopes will be very sensitive to temperature and you will need some way to keep refocusing through the night.

It might be worth looking at one of the CF scopes to get something a bit stronger and less sensitive to temperature. The Skywatcher 250 for example would be a reasonably good match to the pixel size of your camera and might be worth a look - it seems to have been designed as an astrograph, rather than being cobbled together from components originally designed for visual scopes. It would be seeing-limited in resolution and give you about 4x the sensitivity - the same as the 300 mm scopes.

[RobF (Rob)]

It might be worth PM'ing Tandum on this Anthony - he had a 12" Newt tweaked to the n'th degree with reducer/correcter, OAG and all the goodies.

I would argue there are 2 reasons to upsize your aperture that far (12"):
1. Resolution
2. Time

Neither seem to fit you exactly from what you've said, unless this will be a permanent backyard set up? You're halving resolution by persisting with OSC over mono remember. As far as reducing exposure times with aperture, the other alternative is get away from the city to decent skies. Even a small'ish refractor can perform fantastically as the SNR goes up in a truly dark location like Astrofest - as you know. A 12" Newt isn't much fun to move about though?

What about a truss or carbon fibre 10". Orion Optics UK expensive, but wonderful instruments it seems. Upgrade the camera to something like a QSI mono further down the track....


I should have asked - what are your "Dream DSOs" you'd like to image?

[janoskiss (Steve H)]

I'd say stick with the RC. Newtonians will be no match for the RC for deep sky astrophotography. Coma, field curvature... Great visual scopes, not so great for imaging. (They can be made to work well, I know. But you have a pretty good imaging scope already.) Just push the RC8 to its limits while saving up for a bigger RC.

[rustigsmed (Russell)]

Hi Anthony,

As far as the bintel vs skywatcher goes, i have a skywatcher 12" dob (collapsable f5) and a 12" bintel f4. while the mirror quality may be similar the build quality is nowhere near to each other. if i could turn back time i would have ordered a skywatcher OTA instead of the bintel. I am not sure about it being $600 more when i looked it was about $200- $300 more.

I haven't had to make any modifications to the skywatcher dob at all. with the bintel, i have had to order stronger springs, and i am going to get stiffer spider vanes. as it is for imaging i also upgraded the focuser to a moonlite and would've done that on the SW also. there are probably other things i will need to upgrade, if the weather ever clears up so i can use the thing!

you may wish to consider the 10" CF that Ray suggested, or resign to the fact that you are going to have to make some upgrades to it. or just lash out and get something like this http://www.teleskop-express.de/shop/...n-Germany.html or maybe use the 8" RC you have at the moment and save extra for the 16" RC truss to come out and upgrade then!!

[Grimmeister (Anthony)]

Hi Everyone,

Thanks for all the responses, I think from the comments posted I might just be best to stick with the RC8 (will maybe look to upgrade this one day to a bigger one).

I really appreciate everyone taking their time to provide some insight .

Cheers

Anthony