collimation

peregrine

I picked up an ASI071 during the sale, and in its first use the last couple nights I encountered two problems: trouble reaching focus and poor collimation. You can see whaat I'm referring to in the attached jpg. There may be other issues. If you notice anything else, just shout it out.

The scope is an EdgeHD 11 with a hyperstar on a CGX-L. Until now, my imaging camera has been an EOS, which has a perfect record.

With a little more extension, I can fix the focus problem, but I need some advice on collimation. The manual identifies three sets of push pull screws, but doesn't label them. Which is which? Which direction do I turn them to make adjustments? I hate trial and error. How come these cameras aren't adjusted in China? I really think it should be in better shape straight out of the box.

einari

That doesn't look like collimation /tilt issue.

Just sort out the hyperstar-camera distance (it's quite critical), and you're fine.

peregrine

einari, thanks for the reply. I'm at the correct backfocus now, but I'm still seeing some artifacts in the corners I don't like. Whats the best way to get rid of them?

Also, I'm now seeing another, separate artifact, circled in the second attachment. I've checked the glass for lint/dirt and don't find any. Does the glass come out with a spanner? I would have to drop it at my camera shop for sensor cleaning. This almost isn't worth it.

einari

So you have exactly this?

Backfocus (from mounting thread to focal plane): 59.7mm

Anyway I just noticed this of Hyperstar

Maximum Usable Sensor Size: 27mm Diagonal (APS Format)

And ASI071 has 28. 4mm diagonal so your edge might not be perfect.

That latter is dust mote.

You just have to take flats to get rid of it.

peregrine

Yes, I get some vignetting. Not a problem.

So how do I get rid of the "dust mote" permanently? Or is that not possible?

Should I not expect that the camera as supplied would be completely clean?

Who would buy this thing from me should I decide to sell it at some point?

johnp

To get rid of the dust mote try using a bulb blower first, before you touch the glass over the sensor. I use an 8x jewelers eye loop to check for dust on my camera. You would not believe how much stuff is on there that you cannot see by naked eye. Sometimes a very small particle of dust can show up very prominently.

einari

What John said.

So quite normal to have them.

You can clean them but sooner or later (sooner likely) they reappear.

So that's one good reason to take flats.

Btw, here's a tool to find out where they lie:

http://www.ccdware.com/resources/dust.cfm

peregrine

Sent it back to the supplier, and they agreed it needed to be exchanged. The replacement

camera is working just fine. Never hurts to ask I guess.