72ED with Gpcam2 290c focus help please

[Gmx76]

Hi, need some help please.  I just purchased a used Sky-Watcher 72ed, and trying to use it with my GPCam 2 290C with a 2 inch to 1.25 inch adapter.  Problem is I can't get it to focus  I tried the moon tonight,  which is very bright,and only managed a blurry white blob. I've used this camera on a cheap newt and can get better results, so question is do I need to add an adapter to get focus? Tried a 2x barlow but to no avail.  Thanks, Greg

[Tomatobro]

You will need an extension to move the camera further away from the scope. I am guessing that you have the focuser all the way out and the moon is still not in focus. I use a TeleVue 3.5 inch long 2" extension tube that I got from Flo their part number X3C-0009.

You can use a diagonal if you have one instead of the tube. The good news is that Flo have two in stock

Edited November 5, 2020 by Tomatobro
update

[Chefgage]

10 hours ago, Gmx76 said:

Hi, need some help please.  I just purchased a used Sky-Watcher 72ed, and trying to use it with my GPCam 2 290C with a 2 inch to 1.25 inch adapter.  Problem is I can't get it to focus  I tried the moon tonight,  which is very bright,and only managed a blurry white blob. I've used this camera on a cheap newt and can get better results, so question is do I need to add an adapter to get focus? Tried a 2x barlow but to no avail.  Thanks, Greg

This scope would usually be used with a diagonal and then an eyepiece to gain focus when observing visually. For photography you will not use the diagonal obviously but will still need an adapter to gain focus. The idea is to use a field flattener/reducer for this purpose. Skywatcher do a dedicated field flattener (0.8 reducer) but another cheaper method is to use an OVL field flattener (no reducer).

I use the OVL type and can then gain focus using a camera.

Edited November 5, 2020 by Chefgage

[Gmx76]

Ok got it, thanks!

[Gmx76]

On 05/11/2020 at 10:25, Chefgage said:

I use the OVL type and can then gain focus using a camera

Would i need some kind of adapter to fit my GPCam 290c to the OVL flattener?

[Chefgage]

Thinking about this the reason I used the OVL field flattener is because 1 it gives me the correct spacing to get focus on my canon and also to flatten the image.

This spaced distance is correct for my canon camera but might not be correct for your camera. You will still probably want a flattener though. 

So not really sure with your camera. You do have the added advantage though of being able to pull the camera out slightly to give you a bit more distance (I assume you have already tried that though).

[Gmx76]

Yes,  also tried with a barlow barrel, just need another 1cm or so

[fozzybear]

1 hour ago, Gmx76 said:

Yes,  also tried with a barlow barrel, just need another 1cm or so

for the 72ed the total back focus from focuser is around 134mm to the sensor

[Gmx76]

Ok so decided to get a flattener,  and may get a used one of these: https://www.altairastro.com/lightwave-10x-field-flattener-for-f55-to-f625-refractors-291-p.asp

This has a T- thread,  and needs 55mm back focus. My GPCam2 290C has 12.5mm of back focus and has a C thread on the end of the camera, means I need to make up 42.5mm.

So if I order this https://www.firstlightoptics.com/adapters/astro-essentials-low-profile-female-t-thread-to-male-c-thread-adapter.html which is 8mm.

And this https://www.ebay.co.uk/itm/1x-24-35mm-M42-Variable-Extension-Tube-T2-Extension-Length-for-Astrophotography-/203140599311?_trksid=p2349624.m46890.l49292

I should have everything I need right?  

[Gmx76]

Can anyone let me know if the above extender and t to c adapter will work?  Think it should but want to check before I buy more bits.  Thanks