Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

150p DS focus

nightfisher

By nightfisher
in Imaging - Discussion

Recommended Posts

Lonestar70

Lonestar70

Posted
Posted

Hi Jules,

How does part A attach to your SW adaptor?... does it use the T2 thread?

If so then you might try unscrewing part A from part B... then screw part B straight on to the SW adaptor... this would buy you the length of Part A as extra In Travel... it Might just be enough and won't cost you anything to try.

Don't get to downhearted my friend... we have all shared similar experiences with various astro gear and I am sure we will get you sorted for imaging between us.

Failing that... the TS adaptor I linked to would buy you an additional 20mm or so on top of the above extra travel.

Hope this makes sense.

Best regards.

Link to comment
Share on other sites
  • Replies 37
  • Created
  • Last Reply
nightfisher

nightfisher

Posted
  • Author
Posted

Hi Jules,

How does part A attach to your SW adaptor?... does it use the T2 thread?

If so then you might try unscrewing part A from part B... then screw part B straight on to the SW adaptor... this would buy you the length of Part A as extra In Travel... it Might just be enough and won't cost you anything to try.

Don't get to downhearted my friend... we have all shared similar experiences with various astro gear and I am sure we will get you sorted for imaging between us.

Failing that... the TS adaptor I linked to would buy you an additional 20mm or so on top of the above extra travel.

Hope this makes sense.

Best regards.

no that wont work, i have already tried with a low profile 2" to 1.25 adaptor that brings the camera much closer inwards than this idea and still not enough in travel, hence my reluctance to get the TS version as i would only gain a small amount, and this might not be enough....................................................if i want to try imaging i still have my 90mm f500 achro, i went down this route before when i got the ill fated WO 70mm zs, and had nowt but trouble

Link to comment
Share on other sites
Lonestar70

Lonestar70

Posted
Posted

This is very odd... I use a Nikon D90 an my 150PDS with a 2" - T2 nosepiece screwed into the T-Ring and this comes to focus with around 15mm of In Travel still remaining.

The D90 has a back focus distance of 46.5mm... wherase your camera only requires 20mm... this would suggest you needed to be further out ( by 26.5mm )... not closer IN.... all very odd!!.

Silly question... but what are you using as a target for focusing?... the 150 does not like to focus on things much closer than a mile away.

Best regards.

Link to comment
Share on other sites
nightfisher

nightfisher

Posted
  • Author
Posted

focus was tried on lunar surface, so a bit more than a mile, the annoying thing is the same camera and T ring work lovely in my TAL100rs, no issues in that scope

Link to comment
Share on other sites
Lonestar70

Lonestar70

Posted
Posted

Hi Jules,

Well I think that might just be far enough away :rolleyes:

Ok, try this... take the camera away and just leave the sw adaptor in the focuser.

Get a piece of tracing paper, or thin white paper, and tape it to the outer end of the adaptor.

Point the scope at the moon and adjust the focuser for the smallest white dot... you should be able to see this through the paper.

This will tell you where the focal point of the telescope is in relation to the end of the focusers fixed body... so measure this distance.

Your camera focal plane need to be behind this length (Further out) by a few mm to allow the picture to cover the sensor.

If you also subtract from this distance the thickness of the top of the sw adaptor this will give you the available inward travel from the point of focus.

Once you know where the telescope focal point is you should be able to figure out the length of the required fittings to mount the camera... and as long as this length is less than the available focus travel by say10mm or so then you should be able to reach focus with a little to spare.

This is a very strange situation.

Best regards.

Link to comment
Share on other sites
nightfisher

nightfisher

Posted
  • Author
Posted

I think the best plan is to get an engineer to machine the T ring body down a little, then it will fit into focuser tube minus the 1.25 adaptor, giving me a lot more inwards travel

Link to comment
Share on other sites
Lonestar70

Lonestar70

Posted
Posted

Hi Jules,

Yes I suppose that is one way to get your camera mounted, at least it won't mean spending large sums of money.

My main concern is why you need to be so close in with the PDS and the idea of finding where the SCOPE mirrors focused relative to the focuser was to try and determine if there was a possible problem with your particular unit.

Hence the paper test and measurements I suggested.

As has been said, by many of the other guys, it seems very odd that you should need to be that close in with a 20mm back focus camera when others, including me, can get focus with 10mm - 20mm of spare INWARD travel when using cameras of 46mm - 55mm back focus requirement... this just not add up.

Anyway, you have a plan and it is worth trying... If you have any problem finding someone to turn down the addaptor body for you... give me a shout (on here or via PM) and I will be happy to do it for you on my lathe... No Charge... other than the small amount of postage involved.

Keep us informed.

Best regards.

Link to comment
Share on other sites
nightfisher

nightfisher

Posted
  • Author
Posted

Hi Jules,

Yes I suppose that is one way to get your camera mounted, at least it won't mean spending large sums of money.

My main concern is why you need to be so close in with the PDS and the idea of finding where the SCOPE mirrors focused relative to the focuser was to try and determine if there was a possible problem with your particular unit.

Hence the paper test and measurements I suggested.

As has been said, by many of the other guys, it seems very odd that you should need to be that close in with a 20mm back focus camera when others, including me, can get focus with 10mm - 20mm of spare INWARD travel when using cameras of 46mm - 55mm back focus requirement... this just not add up.

Anyway, you have a plan and it is worth trying... If you have any problem finding someone to turn down the addaptor body for you... give me a shout (on here or via PM) and I will be happy to do it for you on my lathe... No Charge... other than the small amount of postage involved.

Keep us informed.

Best regards.

that is very kind of you, will pm you tomorrow

Link to comment
Share on other sites
nightfisher

nightfisher

Posted
  • Author
Posted

New T ring ordered

Bahtinov mask ordered............job done

New T ring ordered.................wrong one! my fault did not check a link and ordered four thirds instead of micro four thirds

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.