Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep28_banner.thumb.jpg.b94278254f44dd38f3f7ee896fe45525.jpg

LightBucket

Polemaster DIY build

Recommended Posts

Hi,

I am thinking of building a DIY polemaster type camera, to be mounted in the same was as the PM but to use the PA tool in sharpcap.

does anyone who owns a PM have an idea what the focal length of the lens is on the PM, as am looking for one with same FOV...I think the camera used in the PM is a QHY5 clone so need to find out the size of the sensor in the PM too, but for now will use an ASI120mm, or a QHY5II camera.

many thanks

Share this post


Link to post
Share on other sites

you can use the asi 120 or qhy5 on a small finder scope, something like 200 mm, and using sharpcap polar alignment tool get as good results as PM, i use it all the time with my 60mm altair astro guide scope and asi camera, then use it for guiding, works a treat.

  • Like 2

Share this post


Link to post
Share on other sites

I also use Sharpcap for PA.

I use an ASI120MC on my AZ EQ6 with a Nikon 50mm f1.8 E series lens at exposures of about 1 second, and have achieved 60 minute subs at 3.5" pp.

pa.thumb.jpg.970bc1e93c3e7af8d6f6c21812073756.jpg

This is a one off test, I captured three frames of L at one hour each, but I regularly image at 30 minutes in Ha with this setup.

m31-deep_3600sec_1x1_L_frame1.thumb.jpg.0cd5ed1c0bc84938604bc530ed195f37.jpg

For my Star Adventurer, I'm using the same camera with a Nikon E series 35mm f2.5 lens using Sharpcap, and can achieved 10 minute subs for widefield.

I have a mind to try it out with a 24mm lens, but have not got round to it.

Hope that helps

 

Huw

  • Like 1

Share this post


Link to post
Share on other sites

You can use a polemaster for easy PA with sharpcap..i PA with postmaster first then load up sharpcap and then it's a few minor adjustments...

I think the polemaster camera is a 5 too..

Edited by newbie alert
Spelling
  • Like 1

Share this post


Link to post
Share on other sites

I see that I am by no means the first to try this idea....

i was trying to find the correct lens to fit to the ASI camera, to give the same field of view as the polemaster...

but the ideas above are superb... :):)

Share this post


Link to post
Share on other sites

Nice idea :)  Horwig, presumably you need to make sure you have the optical axis of the lens/camera well-aligned with the RA axis of the mount?

(I can see no reason why that C-mount lens wouldn't work quite happily, btw.  A lens with an M42 fitting might also do the job, but getting the correct flange-to-sensor distance might be more tricky.  I've never looked at how that works with the ZWO cameras.)

James

  • Like 1

Share this post


Link to post
Share on other sites
7 hours ago, JamesF said:

presumably you need to make sure you have the optical axis of the lens/camera well-aligned with the RA axis of the mount?

No, just that it is pointing within about 5 degrees of the pole.

I had all the bits to use the old Nikon glass on the ZWO, there's no reason that the C mount lenses would not work, I've been considering something similar:

http://www.ebay.co.uk/itm/Fujian-25mm-F1-4-CCTV-TV-Movie-lens-C-Mount-to-Fuji-Fujifilm-X-E2-X-E1-X-Pro1-M1/182381737466?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

 

Huw

 

  • Like 1

Share this post


Link to post
Share on other sites
42 minutes ago, Horwig said:

No, just that it is pointing within about 5 degrees of the pole.

I had all the bits to use the old Nikon glass on the ZWO, there's no reason that the C mount lenses would not work, I've been considering something similar:

http://www.ebay.co.uk/itm/Fujian-25mm-F1-4-CCTV-TV-Movie-lens-C-Mount-to-Fuji-Fujifilm-X-E2-X-E1-X-Pro1-M1/182381737466?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

 

Huw

 

So is the M31 image above taken with the ASI and 50mm lens, or did you just use that for PA..?.

Share this post


Link to post
Share on other sites
50 minutes ago, Horwig said:

No, just that it is pointing within about 5 degrees of the pole.

I had all the bits to use the old Nikon glass on the ZWO, there's no reason that the C mount lenses would not work, I've been considering something similar:

http://www.ebay.co.uk/itm/Fujian-25mm-F1-4-CCTV-TV-Movie-lens-C-Mount-to-Fuji-Fujifilm-X-E2-X-E1-X-Pro1-M1/182381737466?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

 

Huw

 

Edited by LightBucket
Sorry posted this twice...

Share this post


Link to post
Share on other sites

With the fairly small FOV of the polemaster, and the size of the sensor in its camera, I find it must be the equivalent of about a 150-200mm lens in there, but it’s so small, so can’t work out how they do that...! :)

Share this post


Link to post
Share on other sites

The

2 hours ago, LightBucket said:

So is the M31 image above taken with the ASI and 50mm lens, or did you just use that for PA..?.

No, the image is taken with a SX35 camera through a Tak 106, guided with a lodestar and OAG, the ZWO/lens is just for PA

 

2 hours ago, LightBucket said:

With the fairly small FOV of the polemaster, and the size of the sensor in its camera, I find it must be the equivalent of about a 150-200mm lens in there, but it’s so small, so can’t work out how they do that...! :)

according to the 12D string FOV calculator, for the ZWO and a 35mm lens combination, it's giving an FOV of about 7.8 by 5.9 degrees

  • Like 1

Share this post


Link to post
Share on other sites

35mm lens gives an image scale of 57.3/35 degrees per mm and the ASI120 sensor is 4.8mm x 3.6mm, which gives me figures of 7.86 degrees by 5.89 degrees, so the FOV calculator looks good.

The Polemaster apparently has a 25mm lens (to answer one of the original questions) with what appears to be the same sensor giving 11.00 degrees x 8.25 degrees for the field of view, which is consistent with what's on their website.  Given the sensor resolution and pixel size I think it's fairly likely to be a QHY5L-II.  I find myself idly wondering if the Polemaster software wouldn't "just work" if one fitted a 25mm lens to a QHY5L-II, though it may be that they changed the USB PID to make it easier to identify as a Polemaster, in which case the standard drivers wouldn't find it.

Horwig will be getting about 6.5 x 4.12 degrees field of view with the 50mm lens.  Do you think the longer focal length gives you better alignment, Horwig?

LB, I'd forget about "equivalent focal length", by the way.  I've never been convinced that "what size lens would I need on a full-frame DSLR to get the same field of view?" is useful information :)  I don't disagree with your calculation though -- I reckon about 180mm lens on a full frame camera would give roughly the same field of view as the 25mm lens on the Polemaster.

James

  • Like 1

Share this post


Link to post
Share on other sites
52 minutes ago, JamesF said:

Horwig will be getting about 6.5 x 4.12 degrees field of view with the 50mm lens.  Do you think the longer focal length gives you better alignment, Horwig?

Good question, on the ZWO with a 50mm lens it should be about 15" a pixel, I'm assuming Sharpcap is pixel accurate (don't know, just guessing), that's far better than any PA I'm likely to get.

Visually on the laptop screen, the longer lens is easier to use, the display of error between pointing and actual pole is naturally larger.

 

Huw

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, JamesF said:

35mm lens gives an image scale of 57.3/35 degrees per mm and the ASI120 sensor is 4.8mm x 3.6mm, which gives me figures of 7.86 degrees by 5.89 degrees, so the FOV calculator looks good.

The Polemaster apparently has a 25mm lens (to answer one of the original questions) with what appears to be the same sensor giving 11.00 degrees x 8.25 degrees for the field of view, which is consistent with what's on their website.  Given the sensor resolution and pixel size I think it's fairly likely to be a QHY5L-II.  I find myself idly wondering if the Polemaster software wouldn't "just work" if one fitted a 25mm lens to a QHY5L-II, though it may be that they changed the USB PID to make it easier to identify as a Polemaster, in which case the standard drivers wouldn't find it.

Horwig will be getting about 6.5 x 4.12 degrees field of view with the 50mm lens.  Do you think the longer focal length gives you better alignment, Horwig?

LB, I'd forget about "equivalent focal length", by the way.  I've never been convinced that "what size lens would I need on a full-frame DSLR to get the same field of view?" is useful information :)  I don't disagree with your calculation though -- I reckon about 180mm lens on a full frame camera would give roughly the same field of view as the 25mm lens on the Polemaster.

James

All good information for me...many thanks :)

is the QHY5II a 1/3” or 1/2” sensor as that would make a difference 

if it is 1/2” then I will look for one of those as I want to emulate the PM as close as possible... 

also would the FOV of the PM or clone camera and lens, work well with the PA tool in sharpcap, or does that require a larger FOV, as it says in the sharpcap write up to use a finderscope as it needs to see around 15 stars...!

Share this post


Link to post
Share on other sites

The QHY5L-II and ASI120 are 1/3".  The QHY5-II has a different sensor which is 1/2".  The resolution and pixel size given for the Polemaster match the QHY5L-II however.

Any finderscope is likely to have a longer focal length (and therefore smaller field of view) than the Polemaster and probably see fewer stars as a result.  I believe the standard 50mm finder from Skywatcher etc. has a focal length of around 180mm, for example.

James

  • Like 1

Share this post


Link to post
Share on other sites
3 minutes ago, JamesF said:

The QHY5L-II and ASI120 are 1/3".  The QHY5-II has a different sensor which is 1/2".  The resolution and pixel size given for the Polemaster match the QHY5L-II however.

Any finderscope is likely to have a longer focal length (and therefore smaller field of view) than the Polemaster and probably see fewer stars as a result.  I believe the standard 50mm finder from Skywatcher etc. has a focal length of around 180mm, for example.

James

Thanks for that :)

So are you saying that if sharpcap will work with an ASI120 and a finderscope, then it will surely work with a set up equivalent to that of the polemaster..??

Share this post


Link to post
Share on other sites

The other good thing about using a fast photo lens is the speed of getting good PA. Initially, just point the mount roughly North with the compass and inclinomter on my phone, and then with my 50mm f1.8, and a laptop with some grunt I'm getting near realtime feedback to adjustments with exposures of half a second.

 

Huw

  • Like 2

Share this post


Link to post
Share on other sites
23 minutes ago, LightBucket said:

So are you saying that if sharpcap will work with an ASI120 and a finderscope, then it will surely work with a set up equivalent to that of the polemaster..??

I can't see why not.  Sounds like Horwig's works well with a 50mm lens and Sharpcap.

James

  • Like 1

Share this post


Link to post
Share on other sites
15 hours ago, JamesF said:

I can't see why not.  Sounds like Horwig's works well with a 50mm lens and Sharpcap.

James

Can I ask a favour....

if I was to use a camera with only a 1/4” (ASI034mc) sensor, what focal length lens would I then need to produce the same FOV as the polemaster, would it be something like a 15mm...?? Not sure how to work these things out.. :) 

Share this post


Link to post
Share on other sites
26 minutes ago, LightBucket said:

Can I ask a favour....

That's what this forum is all about:icon_biggrin:

 

I use the 12d string FOV calculator,

http://www.12dstring.me.uk/fovcalc.php

 

FLO have one as well, this a bit better, it lists more cameras

http://astronomy.tools/calculators/field_of_view/

Looks like you would need a lens of about 12-14 mm for roughly the same FOV as the Polemaster (15 x 12 degrees)

Sharpcap on their website used to mention a 5 degree search field, but I can no longer find the reference on the updated website

 

Huw

  • Thanks 1

Share this post


Link to post
Share on other sites
5 minutes ago, Horwig said:

That's what this forum is all about:icon_biggrin:

 

I use the 12d string FOV calculator,

http://www.12dstring.me.uk/fovcalc.php

 

FLO have one as well, this a bit better, it lists more cameras

http://astronomy.tools/calculators/field_of_view/

Looks like you would need a lens of about 12-14 mm for roughly the same FOV as the Polemaster (15 x 12 degrees)

Sharpcap on their website used to mention a 5 degree search field, but I can no longer find the reference on the updated website

 

Huw

Thank, isnt the PM 11x8 degrees...!!? :)

Share this post


Link to post
Share on other sites

The PoleMaster is basically a QHY5L-II-M camera (APTINA MT9M034 CMOS sensor) and a 25mm CCTV lens.

This is essentially what I use...
https://wix443.wixsite.com/polemaster-emulator

Or of course SharpCap. But with SharpCap I use my 130mm focal length guide scope instead. The nice thing about 25mm of the PoleMaster is that finding Polaris is very easy, just eyeball it and you will be close, with 130mm, not so easy.

  • Thanks 2

Share this post


Link to post
Share on other sites
17 minutes ago, StuartJPP said:

The PoleMaster is basically a QHY5L-II-M camera (APTINA MT9M034 CMOS sensor) and a 25mm CCTV lens.

This is essentially what I use...
https://wix443.wixsite.com/polemaster-emulator

Or of course SharpCap. But with SharpCap I use my 130mm focal length guide scope instead. The nice thing about 25mm of the PoleMaster is that finding Polaris is very easy, just eyeball it and you will be close, with 130mm, not so easy.

Well, what a star you are, that is superb and exactly what I have been after... :):)

so I guess the file basically tells the software that it is a genuine polemaster camera that is connected rather than a clone..?

did you write that software or another genius....

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.