11 replies to this topic

[Karl S]

Brand new to the hobby, so forgive the incorrect nomenclature I am sure I'm about to use.

 

I am looking for help on how to attach a guide camera to my LX90. The scope doesn't use standard threads that you see on a 1.5" lense (such as how you would attach a filter to a lense) and it doesn't slide out like a standard 1.5 lense either (it threads in).

 

I'm going to buy a ZWO guide camera (so it will work with my ASIAIR Mini), but I can't seem to find the correct way to connect it. I'm sure it's out there, I just can't find it. (Side note, send me a message if your selling one. ...I'll look in the classifieds to).

 

Thoughts?

[Mike7Mak]

Have you set up the scope for computer control? If you intend to guide this will be necessary. Bare bones photography might be possible with the alt-az mount and just the hand control but guiding won't be.

 

Which LX 90 is it, size, year? Do you have the polar wedge? What main camera will you be using?

 

Attaching a guide camera to the finder scope in your picture is not possible without destructive modification of the finder scope and even then it will not be an ideal guide scope.

 

Setting up that scope for astrophotography is a fairly involved project and for any hope of success you will need at a minimum, computer control, an off-axis guider, focal reducer, the polar wedge, knowledge of how to train the drive for periodic error, etc.

 

This obviously involves more subjects than can be covered in a single post. You're also considering starting AP with very difficult type of long focal length scope. It can be done but it won't be easy and satisfactory results won't come fast or be cheap.

 

A little more info about your equipment, knowledge, and goals would be a big help.

[BlueMoon]

Meade had an off-axis guide scope assembly which has been discontinued. https://agenaastro.c...ider-07054.html

Edited by BlueMoon, 18 May 2024 - 09:45 PM.

[Karl S]

Have you set up the scope for computer control? If you intend to guide this will be necessary. Bare bones photography might be possible with the alt-az mount and just the hand control but guiding won't be.

 

Which LX 90 is it, size, year? Do you have the polar wedge? What main camera will you be using?

 

Attaching a guide camera to the finder scope in your picture is not possible without destructive modification of the finder scope and even then it will not be an ideal guide scope.

 

Setting up that scope for astrophotography is a fairly involved project and for any hope of success you will need at a minimum, computer control, an off-axis guider, focal reducer, the polar wedge, knowledge of how to train the drive for periodic error, etc.

 

This obviously involves more subjects than can be covered in a single post. You're also considering starting AP with very difficult type of long focal length scope. It can be done but it won't be easy and satisfactory results won't come fast or be cheap.

 

A little more info about your equipment, knowledge, and goals would be a big help.

I am using an ASI585MC for my main camera. I have a flatener on the way. The telescope is mounted on an equatorial wedge. I am controlling the rig via an ASIAIR Mini. Year wise, it's an older model, not an ACF. Its an 8" LX90. I'll be controlling it via a desktop setup with ASIAIR application. 

 

My goals are both DSO and planetary images. I know that doing DSO with such a long focal length is hard, I don't know why, but I've read enough to know it is. My telescope came from my Dad when he passed away, so that's the gear I'm starting with. I'm more than dedicated and willing to learn. Juat a lot tontake in at first.. 

[Mike7Mak]

Meade had an off-axis guide scope assembly which has been discontinued. https://agenaastro.c...ider-07054.html

I have one of those and almost any newer oag would be a much better solution. That Meade oag is a relic from the manual guided film days.

 

All that's needed to connect to the back of the main scope is an SCT to M42, M48 or M54 adapter depending of the size of the main imaging chip and/or the clear aperture of the visual back. I've been away from Meade scopes for quite a while now and specific details are lost in the mist.
 

[Karl S]

I have one of those and almost any newer oag would be a much better solution. That Meade oag is a relic from the manual guided film days.

 

All that's needed to connect to the back of the main scope is an SCT to M42, M48 or M54 adapter depending of the size of the main imaging chip and/or the clear aperture of the visual back. I've been away from Meade scopes for quite a while now and specific details are lost in the mist.
 

Seems like the preferred choice (over an off axis solution) would be to replace the guide scope. Or am I missing something? 

Edited by Karl S, 18 May 2024 - 09:55 PM.

[Mike7Mak]

I am using an ASI585MC for my main camera. I have a flatener on the way. The telescope is mounted on an equatorial wedge. I am controlling the rig via an ASIAIR Mini. Year wise, it's an older model, not an ACF. Its an 8" LX90. I'll be controlling it via a desktop setup with ASIAIR application. 

 

My goals are both DSO and planetary images. I know that doing DSO with such a long focal length is hard, I don't know why, but I've read enough to know it is. My telescope came from my Dad when he passed away, so that's the gear I'm starting with. I'm more than dedicated and willing to learn. Juat a lot tontake in at first.. 

Sorry about your Dad, lost mine 4 years ago.

 

Ok so you're further along than I assumed at first. As I mentioned using the finder scope for a guider is not easily doable and a separate guide scope is not optimal for an SCT because of the moving mirror focusing system causing differential flexure.

 

Ideally an off axis guider would be the way to go. There are charts on most ZWO camera ads that show how they are set up and many posts here dealing with the usual problems encountered.

[Karl S]

Sorry about your Dad, lost mine 4 years ago.

 

Ok so you're further along than I assumed at first. As I mentioned using the finder scope for a guider is not easily doable and a separate guide scope is not optimal for an SCT because of the moving mirror focusing system causing differential flexure.

 

Ideally an off axis guider would be the way to go. There are charts on most ZWO camera ads that show how they are set up and many posts here dealing with the usual problems encountered.

I won't lie, you lost me. I've been reading a lot over the last few weeks but......you lost me. SCT has a moving mirror and that makes a guide scope difficult?.......yep, you've surpassed my level of knowledge. 

 

Why is an off axis guider preferred over a separate scope and guide camera? 

[Mike7Mak]

I won't lie, you lost me. I've been reading a lot over the last few weeks but......you lost me. SCT has a moving mirror and that makes a guide scope difficult?.......yep, you've surpassed my level of knowledge. 

 

Why is an off axis guider preferred over a separate scope and guide camera? 

Because the SCT focuses by moving the main mirror it always has some necessary play which allows the mirror to 'tip' slightly as the scope tracks across the sky. This causes movement in the imaging camera that's not seen by a separate guide scope. This will produce egg shaped stars and blur the main image. An oag sees the same movement as the imaging camera and guides it out.
 

[Mike7Mak]

In addition a separate guide scope adds significant weight to the top of the scope and will require counterweights (more weight) to offset it. Weight is your enemy on these Meade fork mounts, keeping the scope as light as possible will greatly improve performance. You will probably need some counterweight even with an oag but no where near as much.

[michael8554]

"Differential Flexture" becomes more and more of a problem as the imaging focal length increases.

 

So at maybe 700mm FL and above an OAG becomes a necessity.

[Karl S]

In addition a separate guide scope adds significant weight to the top of the scope and will require counterweights (more weight) to offset it. Weight is your enemy on these Meade fork mounts, keeping the scope as light as possible will greatly improve performance. You will probably need some counterweight even with an oag but no where near as much.

 

So I messed around with an OAG I got in a package deal here. Pretty sure it won't work for my needs as it's very thick and I need to add a diagonal to clear the mount (which would be too much backspace. 

 

Looks like I'll need to buy a new thin OAG and play the fitting game.