Does ASI120 focus in a Coronado PST?

[Astroblagger]

Was toying with the idea of getting an ASI120, would be into doing abit of Ha solar imaging with it, just wandering if it comes to focus in the PST?

[lukebl]

Hard to tell. It seems that some versions of the PST are more receptive to cameras than others. Although I don't have an ASI120, my PST wouldn't focus with any of my cameras without a 2x Barlow. I have subsequently replaced the focuser, so it now will focus with any cam. Expensive business!

[Merlin66]

The new PST for some reason, only known to Meade/ Coronado, has an eyepiece holder 5mm higher than previous!

This makes it even more difficult to fit a camera which has a shouldered nosepiece,

The ASI (and QHY5 II) type body is probably easier to fit as it can/ could be slipped all the way into the nosepiece.

There may be issues with the ASI re. Newton rings in Ha.

[JamesF]

THe ASI120 won't reach focus, no.  I wouldn't be surprised if the QHY5L-II did, though I didn't try mine before I butchered the PST to put a proper focuser on it.

James

[Merlin66]

James,

OK. My error.

I thought the ASI 120 had the same body shape as the new QHY5II

http://www.zwoptical.com/eng/Cameras/ASI120/index.asp

I would have thought the slimline body on the QHY5 II would have allowed the camera to sit far enough in to accommodate the 15mm backfocus....

[JamesF]

No, it's very similar to the original QHY5 in fact.  Perhaps not quite as deep in the body by a few millimetres, but otherwise very similar.

James

[JB80]

This is interesting, how can I tell if my PST is the newer or old one?

My DMK with the short adapter comes to focus fine without any butchering. Would that mean the ASI would still not be able to focus and the QHY would?

I'm trying to pick between the two cameras at the moment and considering the price difference was myself wondering if it was worth considering solar in the equation seeing as the DMK is already a good camera for it.

[JamesF]

Mine is, as far as I'm aware, "new".  The total height of the eyepiece holder is 58mm.

I struggle to imagine that the QHY won't come to focus.  I see no reason that it wouldn't slip down inside the eyepiece holder far enough to get the sensor to the focal plane because there's nothing to stop it doing so.

The ASI120 sensor on the other hand is from memory something like 13mm behind the nosepiece flange.  I believe that is more than the DMK and it won't reach focus as a result.

It's a difficult choice between the QHY5L-II and ASI120 I think.  I'd say that the shape of the QHY makes it more adaptable, but on the other hand I wasn't that impressed that the retaining screws on the rear faceplate of mine started to show signs of corrosion from dew after a number of long nights outdoors when used in a finder-guider (I shall probably replace them with some stainless ones at some point) and I'd say that the firmware is less robust than the ASI.

James

[Merlin66]

Jarrod,

I have details somewhere...let me find them....

You need to measure the  height of the eyepiece holder above the "black box" - I think the "older" version was 57mm and the new version 62mm...

I'll confirm ASAP.

[JamesF]

Is this a very recent change then?  Mine is definitely 57 or 58mm and I'm sure it's less than two years old.

James

[JB80]

Just measured mine and it's 57-58mm too, I have had mine for a few years now. It was one of the first ones when FLO first started stocking them.

It's a difficult choice between the QHY5L-II and ASI120 I think.  I'd say that the shape of the QHY makes it more adaptable, but on the other hand I wasn't that impressed that the retaining screws on the rear faceplate of mine started to show signs of corrosion from dew after a number of long nights outdoors when used in a finder-guider (I shall probably replace them with some stainless ones at some point) and I'd say that the firmware is less robust than the ASI.

James

It is a tough call, I'm finding it really hard to pick if I'm honest. I'm leaning to the ASI I think.

[Merlin66]

James,

I've only become aware of it on the most recent PST's................

[Astroblagger]

I removed my PST focuser and machined 1-2mm off it, focused with a dmk 21 anyway, can these Newton rings be removed with flats or processing?

[JamesF]

can these Newton rings be removed with flats or processing?

Not that I'm aware of.  The solution proposed by ZWO is to use a mechanism that tilts the camera fractionally, but that probably requires a load more backfocus.

James

[lukebl]

I removed my PST focuser and machined 1-2mm off it, focused with a dmk 21 anyway, can these Newton rings be removed with flats or processing?

I found that the best way to lose the Newton's Rings is by allowing the image to drift slightly across the field of view. They then get lost in the stacking process. Obviously, you don't want it to drift too far, or you end up having an insufficient proportion of the frame to stack.

[Astroblagger]

Hmm sounds too much hassle to me, the dmk I had never had any such problems, you just plugged it in and off it went no rings etc,

[Stu_2011]

Hi

The new Atik GP guide camera comes to focus on the new PST's (on mine at least) if you remove the 1.25" nose piece and place the camera on top of the PST eyepiece tube, good size mono chip as well. The sensor is near front of the camera body so that helps.

Stu

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