Pitch Black Skies

Just found a problem with the collimation cap I have been using. 😬

If I rotate it in the eyepiece holder, the peephole doesn't stay exactly in the centre of the doughnut. It isn't very obvious, but under close inspection it isn't perfect. 

I think I have underestimated just how exact collimation needs to be for astrophotography. 

First narrowband image! 🤩

Elephants trunk nebula in Ha

68x300s

I'm after stacking all of the frames and while the master isn't perfect I think the finished result looks more than acceptable.

I might try to pick up a laser again for the primary. I'm not a huge fan of them but if used carefully they have advantages over other methods. It's possible the centre of my doughnut isn't the centre of the mirror. The concentre works great for the secondary.

A second attempt last night.

In live view mode I zoomed in on a bright star. I then put some pressure on the imaging train but the star shape didn't change. This has me thinking it isn't sensor tilt. I then adjusted a collimation screw on the primary mirror while watching the star and it went from elongated to more pinpoint. It seems like a collimation issue. I had it exact before adding the imaging train so I'm not sure what is causing it. I collimate using concentre and collimation cap. I analysed a sub from last night and now it looks like a combination of pinched optics in the top right corner and radial stretching in the others indicating the cc is too far from the sensor. 

Light_IC1396_300.0s_Bin2_294MM_H_gain120_20220814-033125_-10.0C_0023.fit

Any further advice is greatly appreciated, apart from getting an Apo 😌

@pipnina thanks, that's a useful tool.

I managed to pull this from CCD inspector.

CCD 1.fitCCD 2.fit

It seems like it might be tilt and collimation.

I agree with Michael. Top left looks the best to me too.

Collimated before imaging.Light_IC1396_300.0s_Bin2_294MM_H_gain390_20220813-000724_-10.0C_0001.fit

Just now, AstroNebulee said:

Will do Alan 

FITS file coming soon...

294MM

130PDS 

Skywatcher Aplanatic 

20 minutes ago, AstroNebulee said:

Looking at your M31 images shows tilt too, only the bottom right corner looks ok to me when pixel peeping. 

I have the older (longer tube version) and use 64mm of backspacing atm 

Lee

Lee can you take a look at my thread in the imaging section. I'm having a similar problem. I can upload a raw sub for you.

Cheers,

Alan

Could I get an experienced pair of eyes to have a quick look at my sub please?

My stars not round and I'm wondering what could be causing it.

It has been a while, been waiting for this one for a long time.

Andromeda ~4 hours

This is with a 294mm pro and 130pds. I had it set in bin 1 mode accidentally. 

I've gotten odd shaped stars in every single one of my subs. They all look similar. It has happened on each LRGB filter. There isn't any obstruction in the light path. The guiding was reported as .5 total RMS. Does it look like pinched optics? I have recently removed the primary baffle and instead fitted the primary mirror to it's cell with 3 blobs of silicone. I'm wondering if the silicone is preventing the mirror from expanding and contracting as the temperature changes.

Cheers,

Alan

Ah sh..ugar

It was on backwards 🤦😆😆😆

I hope you're right, I'll take another look now.

Thanks Alan,

It seems I must have an older version. I think the buyer said it was about 5 years old.

I hope the extra 1mm won't cause difficulties for me. That would be a right pain.

Edit: it probably isn't that bad actually. I could swap the 11mm spacer for a 10mm one. They should be fairly handy to come by.

Alan 

I've just received a second hand ZWO EAF mini. I did a little Google search to see how to achieve backfocus.

ZWO state the thickness of the mini EFW as 20mm.

I have measured it out of curiosity and have found it to be actually 21mm. That creates a problem for backfocus.

With a T2-T2 adapter included, it should give a back focus of 56mm as they state, with the 1mm extra to allow for a filter's glass. However, you will find it gives an actual backfocus of 57mm. That's an extra 1mm that shouldn't be there.

I'm not sure if it will make a huge difference to images but I'm really surprised how they could have gotten something like this wrong.  Please tell I'm missing something here. Is the Mini 1mm thicker than their other EFWs?

As a quick measurement, it might seem like 20mm but there is a lip on the backplate which must be accounted for too. See pictures attached.

Quick measurement ⬇️

Real measurement including the backplate lip ⬇️

The backplate lip ⬇️

Hi Chris,

You can probably get away with it like that as the sensor is small and very forgiving, however I had my filter as close to the sensor as possible for best practice.

I threaded my UV/IR cut filter into the provided T2-1.25" adapter, then threaded that adapter into the first backspace extension that was threaded to the camera body. This left the filter body about 1mm from the AR glass window.

PM sent 

30 minutes ago, barbulo said:

It’s strange because this adapter they sell is meant for the GPU and the Baader MPCC

I know, I think you think can screw it on but you cannot introduce a camera rotator. I would want the camera rotator for framing.

To be honest, even after a lengthy email discussion I'm still not entirely sure.

I can forward you the discussion if you like. Maybe you can make more sense of it that I could.

A mixture of Startools and Siril.

Do you have the GPU? I enquired about doing with and according to teleskopexpress it isn't possible. I was told the GPU needs more space.

No joy with Startools. I got an okay result with Siril.

Nice image Chris, glad to see you having fun with the camera.

Any chance you could upload the file as .FITS?

I'd like to have a pop in Startools.