Can’t find focus with Coronado PST and ASI cameras?

[CraigD1986]

I know it's possible to image with this scope but I just can't get anywhere near focus. here's what I've tried:

ASI662MC - 1.25" nosepiece inserted straight into the eyepiece holder. I can't seem to get the sensor close enough.

ASI178MM - Same as above.

ASI533MC Pro - Same as above.

Add the lens of a 2x Barlow to the end of the nosepiece - still can't find focus.

ASI120MM Mini - This camera can be inserted all the way into the eyepiece holder but I still couldn't find focus. I also set the gain to 0 and exposure to 1ms but the whole disc was blown out.

Can anyone who uses a Coronado PST for imaging offer any advice?

TIA.

[michael.h.f.wilkinson]

I haven't any experience with the PST, but I did notice a similar issue with the Lunt LS35THa I used to have. I could just reach focus with the ASI130MM I had at the time but it was very tight. Using a tele-centric Barlow (Meade TeleXtender 2x or PowerMate 2.5x) sorted it 

[AstroKeith]

I can get focus with a ASI120 mini. It is inside the eyepiece holder so only similar 1 1/4" cameras can work.

[Elp]

It is possible with a mini type camera, if you did a search you would have found my topic on the matter:

 

 

[Elp]

With the 120, you'll get Newton rings in the image, its inherent from the camera but still possible to use.

[CraigD1986]

Thanks. I’ll have another go with a 120mm mini when the sun comes out

[Planetary Observer]

@CraigD1986, I am successfully imaging using the Coronado PST Double Stack. My camera is the Altair Astro GPCAM3 178c USB3. This comes with a 5mm spacer and 1.25" nosepiece extension, and with both fitted it focuses properly - have a look in the solar imaging section for my recent images. 

[andyrawlins]

FLO are now selling a low profile nose piece for the ZWO planetary cameras (I have a 224 MC) which allows me to easily get focus without a Barlow and just about get a full disc.  Its one downside is that the nosepiece is not threaded for filters, its just baffled, so if you want to use it for normal work you will need to swap it out again.  Its £29 which is a little steep but I guess they have had to commission it specially and it does what it says on the tin!  I've put a full review on the product page: https://www.firstlightoptics.com/adapters/astro-essentials-low-profile-camera-adapter-for-zwo-planetary-cameras.html