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Imaging with the 130pds

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Posted (edited)

M35 cluster in Gemini  |  60min total exposure.

Really proud of this one, especially because of how little time I get to image at any given opportunity.

Give me your opinions! Thanks!

edit: and yes, I know I've got trailing stars, but I really didn't want to give up any exposure time by dropping frames.

M35processed.jpg

Edited by Galen Gilmore
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Posted (edited)
On 05/03/2020 at 23:50, Adam J said:

Difficult choice I got to the point when I was thinking of either getting a moon light focuser or moving onto a refractor, in the end I decided it was a false economy to try putting a £300 focuser onto a £160 scope and saved for the refactor instead. The original focuser is fine for a DSLR or a OSC cooled camera, but by the time its having to hold a dedicated mono camera and a 8 position filter wheel it just cant hack it. The main issue is that you colimate with the light weight colimation tool in it and then the whole thing moves when you put the camera system on and hey presto your colimation is wrong.

Well after a weekend of research it seems there is not an easy solution to my focuser sag problem on the 130PDS. There are just 2 focusers that will fit it seems ? The Baader SteelTrack Diamond (my preferred option) won't fit.

Moonlite - It'll fit but it costs ££££££ especially if adding autofocusing, while reviews seem mainly favourable a couple of people have said it’s no good. 

TS-Optics MONORAIL 2" Newtonian focuser with Micro Transmission – it’s cheaper but fiddly to fit (drilling holes), can’t find any reviews but the spec seems to suggest it’ll be better for my purposes than the stock focuser.

I’m waiting for a reply from TS optics as to whether this one will fit too.

https://www.teleskop-express.de/shop/product_info.php/info/p6522

Tbh, I am starting to wonder whether I should move to a new telescope with a better focuser rather than faffing about trying to fit one into the 130PDS. I’ve been looking at TS optics 6” f4 Newts which have the same two TS focusers mentioned above, trouble is I don’t know how good these focusers are !

Edited by Spaced Out

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14 hours ago, Galen Gilmore said:

M35 cluster in Gemini  |  60min total exposure.

Really proud of this one, especially because of how little time I get to image at any given opportunity.

Give me your opinions! Thanks!

edit: and yes, I know I've got trailing stars, but I really didn't want to give up any exposure time by dropping frames.

M35processed.jpg

Good work ! 👍

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15 hours ago, Spaced Out said:

Well after a weekend of research it seems there is not an easy solution to my focuser sag problem on the 130PDS.

What approaches have you taken to adjusting the focuser?

There are many screws and it is easy to adjust the wrong one. As well as screws holding the spindle block in position (with 0-rings to allow for misalignment) tehre are also scres that adjust the alignment of the focuser spindle which must sit level on the focuser tube flat for maximum effectiveness.

All conventional crayfords rely on solely on pressure from the screw (or screws) that press the focuser spindle against the bearings OR the lock screw. The lock screw is not central to the bearings and may not hold the tube as accurately. Have you tried tightening the spindle adjusters until it starts to go stiff, then backing off a tiny amount?

Also, is it sag or mis-alignment? If the secondary isn't well placed or collimation is off, this can tilt the focal plane.

It's also possible the bearings are mis-adjusted - there are two screws opposite the spindle on the focuser body, these should be set so the tube moves freely and doesn't bind or scrape against the tube.

It's also possible the focuser isn't aligned straight. Each of the three screws holding the focuser body to the mounting plate has a grub screw next to it. Each pair of screws can be adjusted together (slack off the main screw before adjusting the grub screw) to tilt the whole focuser into accurate adjustment.

Most people never need to touch these adjustments, but if your focuser is off, it may be that they need attention.

The reason I ask is I have imaged with very heavy rigs hanging of the focuser with no signs of sag, and with something like 16 screws  that can potentially affect sag or alignment (not allowing for the 13 involved in collimation which could also be a problem) it is pretty easy to run out of patience or ideas before actually tracking down the source of the problem.

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Posted (edited)
8 hours ago, Stub Mandrel said:

What approaches have you taken to adjusting the focuser?

There are many screws and it is easy to adjust the wrong one. As well as screws holding the spindle block in position (with 0-rings to allow for misalignment) tehre are also scres that adjust the alignment of the focuser spindle which must sit level on the focuser tube flat for maximum effectiveness.

All conventional crayfords rely on solely on pressure from the screw (or screws) that press the focuser spindle against the bearings OR the lock screw. The lock screw is not central to the bearings and may not hold the tube as accurately. Have you tried tightening the spindle adjusters until it starts to go stiff, then backing off a tiny amount?

Also, is it sag or mis-alignment? If the secondary isn't well placed or collimation is off, this can tilt the focal plane.

It's also possible the bearings are mis-adjusted - there are two screws opposite the spindle on the focuser body, these should be set so the tube moves freely and doesn't bind or scrape against the tube.

It's also possible the focuser isn't aligned straight. Each of the three screws holding the focuser body to the mounting plate has a grub screw next to it. Each pair of screws can be adjusted together (slack off the main screw before adjusting the grub screw) to tilt the whole focuser into accurate adjustment.

Most people never need to touch these adjustments, but if your focuser is off, it may be that they need attention.

The reason I ask is I have imaged with very heavy rigs hanging of the focuser with no signs of sag, and with something like 16 screws  that can potentially affect sag or alignment (not allowing for the 13 involved in collimation which could also be a problem) it is pretty easy to run out of patience or ideas before actually tracking down the source of the problem.

Thanks for this.

I’ve tensioned the spindle as much as I can but that is limited by the SW autofocuser that slips if I tighten it too much. I don’t use the lock screw because I have the autofocuser fitted.

I haven’t touched the 3 focuser collimation screws. It came to me direct from the factory and works well with DSLRs so figured there’s no need. The weight of my mono + filter wheel combo is the issue here. I have gravitational movement of the focuser tube that then leads to coma like stars along one edge of the image. I can replicate this if I place a laser collimator in the tube and then put some pressure on the end to press it downwards, you can see the laser dot move around the primary donut.

The secondary is well aligned (I used a TS Concentre for that) and general collimation looks to be bob on to me.

If I could tighten the spindle tensioner any more I would but then the SW autofucuser just slips and is useless. 😕

Edited by Spaced Out

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5 hours ago, Spaced Out said:

If I could tighten the spindle tensioner any more I would but then the SW autofucuser just slips and is useless.

Have you seen this document (google found it somewhere on here, I can't find the thread):

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=301468

Near the end it explains how the teflon block adjusting screws, if too tight, can cause slippage when you tighten the pressure screw.

 

 

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16 minutes ago, Stub Mandrel said:

Have you seen this document (google found it somewhere on here, I can't find the thread):

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=301468 1002.79 kB · 711 downloads

Near the end it explains how the teflon block adjusting screws, if too tight, can cause slippage when you tighten the pressure screw.

 

 

Thanks, it's useful, tbh I've been through all of that many times now.

I think the real issue is tensioning the focuser so that it works well with the SW autofocuser. The SW autofocuser is a fickle thing, if you tension the focuser so the tube is held tighter (and I presume, less likely to sag) then the SW autofocuser just slips on the spindle and won’t turn it. I find that to use the SW autofocuser and prevent it from slipping on the spindle you have to ease off the focuser tension and then it seems that with a heavy load the focuser tube can move a fraction.

I've got the SW autofocuser set up now so it will lift my 1.3KG camera (+ filter wheel, OAG etc), if I ease off the focuser tension the focuser tube will just slip, if I increase the tension the autofocuser will slip on the spindle. Trouble is this current tension isn't enough to stop movement of the focuser tube when the heavy camera is put on there, so I get this slop/sag.

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On 09/03/2020 at 04:21, Galen Gilmore said:

M35 cluster in Gemini  |  60min total exposure.

Really proud of this one, especially because of how little time I get to image at any given opportunity.

Give me your opinions! Thanks!

edit: and yes, I know I've got trailing stars, but I really didn't want to give up any exposure time by dropping frames.

M35processed.jpg

Good job. Knowing your weaknesses are the key to future success. I appreciate your effort (I am in the same boat) and being self critical is the first step to better images. You are a long way toward getting great images, some of it is opportunity, some financial, most planning and practice. Keep it up and I am sure you will be getting great results.

Marvin

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Depends on how much you need the fine focusing cr2 moonlight when you can get a cr1 moonlight For £200.00 including fiting kit which would cost a £150.00 less

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11 hours ago, mike chadwick said:

Depends on how much you need the fine focusing cr2 moonlight when you can get a cr1 moonlight For £200.00 including fiting kit which would cost a £150.00 less

Thanks, I guess I will need fine focus and autofocus for imaging and with moonlite that means £££££...... Unfortunately there don't seem to be many (if any ?) other options for the 130 PDS and I've read on here one or two people saying they were underwhelmed by moonlite focusers so that makes me nervous. 🤔

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Posted (edited)

I never needed to change the focuser on my 130PDS, the only thing I done was change the focuser collar to a thinner version so my focuser tube does not need to rack in further which protrudes into the light cone, but also it looks like skywatcher might have shortened the draw tube length as mine looks shorter then my previous 130PDS versions.

Edited by Skyline
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20 minutes ago, Skyline said:

I never needed to change the focuser on my 130PDS, the only thing I done was change the focuser collar to a thinner version so my focuser tube does not need to rack in further which protrudes into the light cone, but also it looks like skywatcher might have shortened the draw tube length as mine looks shorter then my previous 130PDS versions.

Thanks. Are you using a SW autofocuser and how heavy is your camera + FW etc ? 

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Posted (edited)

Hi

I have a manual focuser, it's my hands 😀, I am using a Baader coma corrector with 58mm back spacing with a ZWO ASI294MC Pro camera.

I do remember someone on sgl buying a feather touch focuser for the  130PDS. But for any premium focuser upgrade I would rather by another scope.

Edited by Skyline
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Just now, Skyline said:

Hi

I have a manual focuser, it's my hands 😀, I am using a Baader coma corrector with 58mm back spacing with a ZWO ASI294MC Pro camera.

Thanks

I think the issue for me is probably the added weight of a heavy filter wheel + OAG all hanging off a rather fickle SW autofocuser. I don't have tilt problems with the DSLR and I suspect OSC cameras would be less of a problem too as they don't carry that added weight of a FW. 

 

 

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Posted (edited)

I take it you have tried tightening the grub screws underneath the stock focuser?

Mind you using a non reducing corrector does protrude much more out then using the 0.9x corrector which only leaves 5mm to focus with.

Edited by Skyline

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11 minutes ago, Skyline said:

I do remember someone on sgl buying a feather touch focuser for the  130PDS. But for any premium focuser upgrade I would rather by another scope.

I am slowly coming around to this way of thinking....... Trouble is whichever route is taken it means £££££ !

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2 minutes ago, Skyline said:

I take it you have tried tightening the grub screws underneath the stock focuser?

Yes, but I'm limited by the SW autofocuser, I just don't think it is designed for holding/lifting heavy camera gear.

15 hours ago, Spaced Out said:

I think the real issue is tensioning the focuser so that it works well with the SW autofocuser. The SW autofocuser is a fickle thing, if you tension the focuser so the tube is held tighter (and I presume, less likely to sag) then the SW autofocuser just slips on the spindle and won’t turn it. I find that to use the SW autofocuser and prevent it from slipping on the spindle you have to ease off the focuser tension and then it seems that with a heavy load the focuser tube can move a fraction.

I've got the SW autofocuser set up now so it will lift my 1.3KG camera (+ filter wheel, OAG etc), if I ease off the focuser tension the focuser tube will just slip, if I increase the tension the autofocuser will slip on the spindle. Trouble is this current tension isn't enough to stop movement of the focuser tube when the heavy camera is put on there, so I get this slop/sag.

 

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If its truly a moonlite, buy the focuser s/h and buy the mounting plate new.

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Posted (edited)

By installing a stepper focuser, such as the ZWO EAF or Pegasus Focuscube, wouldn't the connecting pulley provide extra stability and prevent a certain amount of slippage because its connected to the focusers' stepper motor, which doesn't move unless commanded to?

This also has the obvious added benefit of giving you accurate focus ability.

Edited by mAnKiNd
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2 hours ago, mAnKiNd said:

By installing a stepper focuser, such as the ZWO EAF or Pegasus Focuscube, wouldn't the connecting pulley provide extra stability and prevent a certain amount of slippage because its connected to the focusers' stepper motor, which doesn't move unless commanded to?

This also has the obvious added benefit of giving you accurate focus ability.

Yes it does. With any motor focuser, you don't use a focus lock, the motor's stall torque takes care of locking.

I found the SW geared dc motor good enough to keep a dslr in place, but it had terrible backlash. The Pegasus focuscube, with its stepper motor, is much better in this respect. It can also hold a camera, efw and oag without any problems.

A focuser doesn't need to be the best on the market, it just needs to be good enough for its purpose. Although I have no experience with it, I would probably go with the TS focuser & plate. I think that if it can hold up to 4 kg in place, it's good enough. But check whether you need to drill new holes for the plate. That could become an issue.

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2 hours ago, mAnKiNd said:

By installing a stepper focuser, such as the ZWO EAF or Pegasus Focuscube, wouldn't the connecting pulley provide extra stability and prevent a certain amount of slippage because its connected to the focusers' stepper motor, which doesn't move unless commanded to?

This also has the obvious added benefit of giving you accurate focus ability.

Thanks. I was considering upgrading the autofocuser to try and tighten things up a bit. I suspect the SW autofocuser may be the weak link for me. I was looking at this.

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/primaluce-lab-sesto-senso-v2-robotic-stepper-focus-motor.html

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5 hours ago, Spaced Out said:

Yes, but I'm limited by the SW autofocuser, I just don't think it is designed for holding/lifting heavy camera gear.

When you say 'it slips on the spindle' do you mean:

The spindle turns but the focuser tube doesn't move.

The autofocuser turns but the spindle doesn't rotate and the tube doesn't move.

The autofocuser doesn't turn and the stepper 'skips' steps?

If the second of these the universal joint between stepper and spindle needs to be tightened up.

 

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2 minutes ago, Spaced Out said:

Thanks. I was considering upgrading the autofocuser to try and tighten things up a bit. I suspect the SW autofocuser may be the weak link for me. I was looking at this.

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/primaluce-lab-sesto-senso-v2-robotic-stepper-focus-motor.html

The ZWO one is very good and doesn't carry the 'Prima Premium'.

It si abit tricky to mount (I had to shorten the mounting bar by 2-3mm)

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5 minutes ago, wimvb said:

Yes it does. With any motor focuser, you don't use a focus lock, the motor's stall torque takes care of locking.

I found the SW geared dc motor good enough to keep a dslr in place, but it had terrible backlash. The Pegasus focuscube, with its stepper motor, is much better in this respect. It can also hold a camera, efw and oag without any problems.

A focuser doesn't need to be the best on the market, it just needs to be good enough for its purpose. Although I have no experience with it, I would probably go with the TS focuser & plate. I think that if it can hold up to 4 kg in place, it's good enough. But check whether you need to drill new holes for the plate. That could become an issue.

This is good to hear ! I may upgrade the SW autofocuser to a better stepper motor then, that should allow me to tighten things up a little with the focuser tension at the same time (I hope).

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2 hours ago, mAnKiNd said:

By installing a stepper focuser, such as the ZWO EAF or Pegasus Focuscube, wouldn't the connecting pulley provide extra stability and prevent a certain amount of slippage because its connected to the focusers' stepper motor, which doesn't move unless commanded to?

This also has the obvious added benefit of giving you accurate focus ability.

I would warn you that for any of those models (I used the focuscube) you will need to modify the 130PDS focuser to allow connection as the body of the auto focuser interferes with the spider vane thumb screw. You need to cut down the pin and mount the auto focuser upside down. I got that model in the knowledge that I was going to be moving it over to the esprit 100. But to be honest for the 130PDS this is best unless you are willing to modify your focuser. 

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/primaluce-lab-sesto-senso-v2-robotic-stepper-focus-motor.html

Adam

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