Is my telescope suitable for planetary?

[edarter]

Now that I'm getting my astro mojo back I'm looking for a 2nd setup more suitable for planetary than deep sky. I have a home made scope (reflector) I bought off a friend a few years ago which has apparently got very high quality glass for the mirror (1/4 wavelength rings a bell but not sure if that is good or not). The mirror does need recoating though. I'm thinking that it might be an idea to use this second scope as a planetary one with its longer reach than my 130pds but not sure if the specs are appropriate. Could those in the know planetary wise have a glance over the below and let me know please?

Mirror dia - 222mm

Focal length - 1285mm

Focal ratio - 5.78

Focuser is 1.25 inch. I'm looking to upgrade it anyway but would it be advantageous to go to a 2 inch one?

My camera is an AA 26c, though I do have a canon Eos 600d astro modded as well.

Thanks

Ed

[CraigT82]

Yeah you can get decent images with a ~9” scope, that is plenty of aperture. 
 

1.25” focuser should be fine in principle but needs to be solid to keep collimation and also capable of minute focus adjustments. 
 

Not sure if the 26c will make a good planetary cam. Can you run it on usb power so the fan doesn’t run and cause micro vibration? 
 

For what it’s worth I had a 220mm Fullerscope newt a few years ago and got these with it…. 

Edited Saturday at 07:23 by CraigT82

[Fegato]

I think one rule of thumb is to aim for 5x pixel size = focal ratio.   So with 3.76 and 5.78 you're well short of that, which will mean you'll struggle to get much detail.  I guess if you could throw in a good barlow, that would improve things?  A dedicated small pixel planetary cam would also help.

[edarter]

1 hour ago, CraigT82 said:

Yeah you can get decent images with a ~9” scope, that is plenty of aperture. 
 

1.25” focuser should be fine in principle but needs to be solid to keep collimation and also capable of minute focus adjustments. 
 

Not sure if the 26c will make a good planetary cam. Can you run it on usb power so the fan doesn’t run and cause micro vibration? 
 

For what it’s worth I had a 220mm Fullerscope newt a few years ago and got these with it…. 

 

 

 

 

 

 

 

Thanks for the response Craig, as it happens this is also a fullerscopes newt! My friend built it to get him through his astrophysics degree. I have one of their old equatorial mounts to go with it but don't plan on using that.

Focuser will need changing, no micro adjustment or anything so that's a definite upgrade needed.

Those images are excellent, gives me hope I'm thinking of the right path. The 26c needs proper power though as it's tec cooled. Would any vibrations be worse than for deep sky then?

Ed

[edarter]

7 minutes ago, Fegato said:

I think one rule of thumb is to aim for 5x pixel size = focal ratio.   So with 3.76 and 5.78 you're well short of that, which will mean you'll struggle to get much detail.  I guess if you could throw in a good barlow, that would improve things?  A dedicated small pixel planetary cam would also help.

Ah ok, will have a look at this aspect then. Might be worth having a go but don't expect good results. Was more worried the scope would not have enough reach. Sounds like that's not a issue from Craig's post but the camera could be a showstopper. Barlow will halve the light won't it?

Thanks

Ed

[CraigT82]

14 minutes ago, edarter said:

Would any vibrations be worse than for deep sky then?

Yeah potentially. With long exposure imaging the other sources of blur are much more damaging (seeing/tracking) so the blur intoduced by vibration goes unnoticed. With lucky imaging you are bypassing the seeing and tracking errors (ant least you’re hoping to) with short exposures and so the micro vibrations can become a significant source of blur. 

[Astronomist]

12 minutes ago, edarter said:

Barlow will halve the light won't it?

This doesn't matter for planetary, almost every great planetary image you've seen would have been taken with a barlow/ focal extender of some kind.

[edarter]

13 minutes ago, Astronomist said:

This doesn't matter for planetary, almost every great planetary image you've seen would have been taken with a barlow/ focal extender of some kind.

Ah ok, interesting!

[Fegato]

yes planets are bright, light is not the issue - size / resolution is the issue! (and seeing I suppose... ADC is another consideration, although with Jupiter and Mars going high at the moment, perhaps not an issue right now)

[CraigT82]

1 hour ago, edarter said:

Barlow will halve the light won't it?

Yeah it doesn’t really matter as the planets are so bright. It’s more important to fully sample all the detail available from the scope. From memory for my images above I used a 2.7x barlow, and the scope was f7.5 so was operating at about f21, way beyond the 5x pixel size rule of thumb. 

Edited Saturday at 10:34 by CraigT82