Vinnyvent84

6 hours ago, michael8554 said:

An image taken looking towards the prism and imaging camera would be instructive.

Michael

Like this? 

40 minutes ago, Elp said:

This person seems to have had a similar issue but didn't post a solution:

https://www.cloudynights.com/topic/706903-oag-prism-blocked/

I’ll check it out. Thank you Elp. 

41 minutes ago, Hals said:

That is definitely orientated correctly.

Depending on your main imaging camera sensor size you may be able to lower the prism further into the light path.

As others have said you can check by doing flats looking for the prism shadow (which calibrates out anyway).

I have a similar issue to you with a very small portion of my OAG view vignetting (Edge 8HD, Celestron OAG\0.7 reducer & 174MMMini) but it does not cause any problems guiding. 

I never have any issues with the 174 in that regard and can always do multi-star guiding.

Pete.

Thanks Pete. So far it hasn’t caused an issue but I did notice if that the main guide star with the box around it in the ASIair encroaches too much in the vignetted area it will flicker back and forth to guide star lost and guiding. Not every time but it’s happened. 
 

I cannot lower it any further unfortunately. There’s a backstop on the prism track that lets you adjust it. If you loosen the grub screw to much you can in theory go past the backstop to get it deeper into the OAG body but you will not be able to properly tighten it back down and the prism will / can fall out. 

18 hours ago, Elp said:

It may or may not be the issue but looking at that photo it looks to me the prism isn't orientated square to the telescope side, see the illustration in this post:

https://www.cloudynights.com/topic/771429-which-side-of-the-off-axis-guider-faces-the-telescope/

 

I took off the camera side. I do have it oriented correctly I believe. The 45 angle is facing away from the scope toward the camera 

4 hours ago, Elp said:

It may or may not be the issue but looking at that photo it looks to me the prism isn't orientated square to the telescope side, see the illustration in this post:

https://www.cloudynights.com/topic/771429-which-side-of-the-off-axis-guider-faces-the-telescope/

 

Now im definitely confused lol per celestrons instructions manual the flat side of the prism faces the telescope while the angled side faces the camera chip. The link attached shows a diagram saying the exact opposite of celestrons instructions?

On 28/05/2024 at 14:04, david_taurus83 said:

The Celestron OAG is a great unit but the stalk is a bit short. See below pic of mine when used with the correct 0.7 Edge reducer for my C8 Edge HD. The prism looks like it would barely pick up any light through the reducer. That said, I have no problem getting guide stars across the chip of my ASI174 mini. The sensor is massive compared to other guide cameras. How does it look if you look at it like below with your reducer?

20 hours ago, Elp said:

If you can, you've got quite a bit of room to push it down further.

This is the furthest down I can get the prism. And here is the  best way I could get the view I believe you guys asked for. In addition, here’s a view of guiding screen last night in the ASIAir. You can see the gradient going from light to almost pitch black when you get to the left end. 

17 minutes ago, Elp said:

If you can, you've got quite a bit of room to push it down further.

I’ll see how much more I can push it down as soon as I’m home and let you know 👍

8 hours ago, Elp said:

If you could take a few exploded images of the individual bits split apart with the prism and main imaging sensor in view it may help us diagnose.

 

I’ll get this for you tonight!

7 hours ago, Elp said:

I think this is your issue, all the images I've seen of that part show it assembled this way below which makes sense, most tapered flatteners also orient like this, fat end on scope, thin end camera side, you might have the OAG on the wrong way though I don't know how due to prism orientation unless it's removable and can go back in both ways looking front and back:

I believe that’s due to the fact it’s the edge SCT which utilizes a different reducer. I’m using a standard C8 with the celestron 0.63 reducer. I never actually removed the prism; only made vertical adjustments and I have the flat side of the prism facing the OTA. 

4 hours ago, Mr_Cat said:

Looking on Flo that photo is of an adaptor for the larger SCT's with a 3.25" SCT thread and using with a full frame cameras
 

Here is my 925 with .63 reducer and Celestron OAG. To get the OAG to work with the reducer I've had to move the prism housing as far as I could into the light path - but my prism housing seemed to have an end stop so when I loosened the allen bolt it only moved "so far" - no risk of it falling out despite what the instructions say..
 

Looks remarkably similar to mine!
 

It does! I notice a key difference though. Your guide camera is much further into the OAG than mine. Perhaps that’s my issue. I originally thought having the spacer in front of the main imaging camera was impacting the stance requirements that need to be match in relation to the guide camera, the main and the prism. But if you’re having no issues and you have the spacer located in the same spot then I guess I can rule that out. 

3 hours ago, Elp said:

So it's likely looking at that flanged piece. Does that OAG have prism tilt adjustment as that may help, my radial guider does.

I’m not expert but I do not believe it does. I just see the grub screw that can be loosened to move the stalk vertically in either direction. 

3 hours ago, david_taurus83 said:

The Celestron OAG is a great unit but the stalk is a bit short. See below pic of mine when used with the correct 0.7 Edge reducer for my C8 Edge HD. The prism looks like it would barely pick up any light through the reducer. That said, I have no problem getting guide stars across the chip of my ASI174 mini. The sensor is massive compared to other guide cameras. How does it look if you look at it like below with your reducer?

I only have this picture currently but I’ll be home from work soon to take the one your requested. I hope it helps. If memory serves I have the stalk down as far as it will go. If it’s not there is only a minuscule amount more I can lower it of that I’m sure. I appreciate the help on this!

13 hours ago, bosun21 said:

The Celestron 0.63 reducer is not suitable for Edge SCT's apparently? This is what some suppliers are indicating.

 

That’s correct. I’m using the non edge sct. It’s just a regular C8 that came on the evolution mount. 

14 hours ago, Elp said:

Are you using an Edge HD8 as it doesn't look like the reducer for that scope. It also looks like it's screwed on the wrong way around, reducers normally scope side are fatter then taper in camera side.

Hey Elp, nope it’s a none edge - standard C8. It’s a Celestron 0.63 reducer. It’s screwed on correctly as it only has only one side that will correctly attach to the rear of the OTA. The image posted by bosun is the one that I have. 

4 hours ago, Elp said:

Looking down the OAG side, what's that dark semi circular shape on top of the illuminated circle (bottom half)?

Actually come to think of it it may just be the prism stalk and it looks that way due to the perspective of the angle I was holding the cell phone. If you look closely I’m coming in at a higher angle I think and pointing it downward so that may be the reason it looks that way. 

5 hours ago, knobby said:

Have you tried the OAG while not connected to the scope to see what it looks like ? I seem to remember my 8 inche HD reducer made the image circle smaller, maybe worth checking OAG in different ways of connecting ?

Sorry if I sound silly but can you please elaborate? How can I check it while not connected to the scope? 
 

I know the image circle on an 8 SCT does shrink when using a reducer but to what amount I honestly do not know. 

4 hours ago, Elp said:

Looking down the OAG side, what's that dark semi circular shape on top of the illuminated circle (bottom half)?

Honestly I have no use lol there’s nothing in the OAG but the prism itself attached to its stalk so I’m unsure what’s causing that. There’s no debris or loose pieces of anything and I wore surgical gloves when I made the adjustments. 

5 hours ago, knobby said:

Are you using a diagonal with the OAG ?

Nope no diagonal being used. Here is a picture of the imaging train. 

11 hours ago, Elp said:

Note when using the focus mode it's a zoomed in view due to the camera and screen needing to update quickly so that might explain why you see the power line shot in full view rather than cut off.

You have tried rotating the camera around the central axis of the OAG haven't you? The adjustment should be there so you can align the OAG prism square with one of the sides of your imaging sensor. The way to do it initially is do it physically with the OAG+spacers+imaging camera off the scope and make sure it's square and just off the edge of your main imaging sensor, then mount to your scope and refine. Either you can rotate the prism stalk part or you could rotate the imaging camera.

Thank you for the reply Elp. Yes I have tried rotating the camera around the central axis and prior to mounting the imaging train to the scope I ensure the prism was squared with the long side of the sensor on the main imaging camera. But the thing is the main imaging camera chip is tiny because it’s a 678mc planetary camera so the prism, even when it’s as far into the OAG as possible doesn’t even come close to getting near the sensor edge. 
 

Thanks for the observation about focus mode view I didn’t know that and it is good to be aware now. However, if you see the guiding view with the green cross hairs notice the gradient of black background. It goes from a lighter black on the right to a pitch black on the left; same location I think the sensor gets “cut off” at. If a star enters that error the guiding will stop as it says guide star lost. 

I even took the guide camera out and tried pointing my cell phone camera in the hole to see the view and this image is the best I could get - not sure what to make of it. 

Hoping everyone can take a look and give some advice on this as I’m a newbie and I’ve tried so hard to get this sorted out but to no avail. 
 

I just put my 8 SCT on my new AM5. I know from my reading that at that focal length it’s advised to use an OAG. In addition from what I’ve read it’s best to use the Celestron OAG as it has a large format prism of 12.5mm and matches mixed with the larger sensor of the ASI174mm mini. So I purchased both. Added them to my imaging train on the 0.63 reduced SCT 8. 
 

I know I have proper back focus of 106mm (added 1mm to account for filter). I read that it’s best to do flats as a test to ensure that the prism is not intruding on the main cameras chip; now honestly that is not needed because I’m only using a 678mc planetary camera as the main imaging camera as I await delivery of my 533mc. As expected no intrusion but this is when things get weird. 
 

I ran a test flat on the guide camera. And it displayed what seems like the sensor getting cutoff to the left. Seems like only 80% of the sensor is getting light. I then dialed up the gain like crazy and you can see that as well in one of the images below. In addition I took a screenshot of the focus tool in the ASIair and you can tell in that image it’s very dark to the left. 
 

I literally adjusted that prism all the way from one extreme to the other along with different movements of the camera in the helical focuser of the OAG. I put the prism of the OAG so deep inside the OAG that it almost fell out. I can’t understand how I wouldn’t be getting use of the whole sensor. But then when I go outside and Focus on a power line for example it looks like the whole sensor is being used. It’s baffling.  Any advice that someone can give would be massively appreciated. Thank you! 

11 hours ago, 900SL said:

For exposure with a 533MC Pro, aim for 3000 ADU average at 100 gain which you can find in the histogram data. This will ensure you are not clipping, and not overexposing. 

Thanks for the info! So I understand the gain; and u understand the clipping part but forgive me for sounding dumb I’m totally clueless in regard to “aim for 3000 ADU average”. What exactly is that and how would I determine that I’m averaging that 3000 number? 

20 hours ago, Hughsie said:

A great resource for research is Astrobin. If you haven’t heard of it it's a community of photographers who post their images/have forum discussions. It is free to join. You can search by location, say New York, and view images posted by individuals near you. In the main they will list the equipment used and exposure times. You can also search by equipment such as your camera and view images and see what camera settings have been used.
 

It’s a great way to see first hand what combination of equipment/exposure times will produce and to look for potential targets. Worth a look if you haven’t already.

Awesome thank you so much that’s great info I’m going to do some searches this evening! 

1 hour ago, Hughsie said:

Hi Vinny.

You are correct regarding darks. These can be captured in advance and are not affected by changes to the image train. What you do need to remember is that your darks need to be captured using the same exposure time, Gain, Offset and Temperature as your light frames. I have a 'Dark' Library for my ASI1600mm and ASI294mc all at a temperature of -10c. For each camera I have exposure times for 60s, 120s, 180s and 300s. The Gain and Offsets for the 1600mm are based on whether I am doing narrowband or broadband imaging. For the 294mc I tend to use a Gain of 121 and offset of 30. I refresh mine every 12 months.

It's best practice to take flats after every session to ensure the best calibration outcome. You can use flats from previous sessions only if your image train has not changed and assuming you keep your optics free from dust. As you mention, changing the image train between capturing your lights and taking your flats will result in poor calibration so don't touch anything. 

In regard to the filter wheel, as you take your flats for each filter the wheel will rotate round and your filters will be in the same orientation as they were when you captured your light frames so this doesn't impact the image train. The only way this will not be the case is if you alter your image train by moving the filter wheel or unscrew the filters and put them back in again. As to the rotation of the wheel moving dust, you would have to be pretty unlucky for this to happen, however, it does no harm to periodically inspect your optics to ensure no dust or other particles have snuck their way in.

Hope this helps.

John

John, thank you so very much. This is extremely helpful. I have ALOT to learn and my gear gets here on Monday. I have a ASI533MC and am pairing it with a Redcat 71 WIFD ASIair Plus and AM5. Your information most definitely helps. 
 

Im currently trying to research how long my sub exposures need to be considering I’m in a Bortle 8 and using OSC. This, along with many other things - but you now scratched one concern off my list so thank you again!  

Hey all, forgive me if this is a silly question…. I’m trying to get started soon with taking a shot at AP. My limited knowledge is that when it comes to darks you can make a library of those generally refreshing every 3-6 months or as needed. And the remainder of calibration frames must be done on a per session bases. 
 

In addition from what I understand - you cannot touch the imaging train in anyway in relation from when you take the calibration frames to doing the actual imaging run. So for example if I was taking flats - I would not be able to alter or touch the imaging train in any way as that may move around dust and render the flats useless? If this is the case how do things work in relation to a filter wheel? 
 

I have read people taking alternating subframes between different filters when doing mono for example. Does the rotating of the filter wheel not constitute “touching” the imaging train during a session? I would think that just the movement of the wheel could introduce new dust or relocate existing dust particles if your bouncing between filters on the wheel from frame to frame? I’m I understanding this incorrectly?

Hey everyone, maybe someone has some ideas on what’s causing this. 
 

I’m using Sharpcap Pro on a Beelink SE12; the computer is brand new essentially. About a week ago I tried doing some lunar imaging using my ASI533MC. I know this is a DSO camera but I figured couldn’t hurt. When I took a 2 min clip and tried to load it into AutoStakkert it generated some weird banding as seen below. 
 

I tried to tweak my exposure to 7ms and have auto white balance on. Biggest ROI for the camera. I don’t know or think the camera is broken because I took it outside during the day and no issues. I also changed the USB cable. 
 

Today I tried again 3 more times. Can you all take a look and give me your thoughts as to the issue? Thanks in advance.