SW PDS focuser tube

[+Stu]

Hi folks. I'm having egg star issues. Seems to be in one particular quarter of my images. My M48 EOS adapter does have a little bit of play in it but I've seen lots of posts about the PDS focuser tube sticking out into the OTA causing issues, the fix being chop a few mm off the end. I'm not overly keen on taking the focuser to bits and cutting bits off it, but if it will improve things enough then I guess it's worth doing. 

Anyone out there with/had a PDS and can advise if it's something that "needs" to be done? Or just a bit of knowledge in general regarding things obstructing the OTA?

[8472]

I stripped down and flocked my 130P-DS only a couple of days ago. Been meaning to do it for years.

 

As you mention, the focuser tube can cause Pacman stars.

 

Chopping a bit off will help this, but then should you need to rack the focuser out for visual, you're stuffed. Also, depending how long you want to keep your scope for, it might impact resale.

 

For now, I chose to leave as is, and fix in post.

 

Not tried it myself, but maybe a 3d printed primary cell clip aperture mask might help a little? It will slow down your scope, though.

 

Kev

[+Stu]

Thanks very much. I use it for visual as well so don't want to impact that. Also don't want to slow it down,  think it can stay as is. 

18 minutes ago, 8472 said:

I stripped down and flocked my 130P-DS only a couple of days ago

Do you have to remove the secondary mirror?

[Bottletopburly]

If you use a skywatcher cc 0.85 I think it is you can do a modification on it so it goes into the tube further this then means you have to rack outward apparently this works didn’t know it at the time , have a look  at Astroblokes channel on YouTube he done it on a 130pds 

[+Stu]

1 hour ago, Bottletopburly said:

have a look  at Astroblokes channel on YouTube he done it on a 130pds 

Will do, thanks very much

[8472]

1 hour ago, Bottletopburly said:

If you use a skywatcher cc 0.85 I think it is you can do a modification on it so it goes into the tube further this then means you have to rack outward apparently this works didn’t know it at the time , have a look  at Astroblokes channel on YouTube he done it on a 130pds 

I didn't know that, David.

 

I've the SW 0.9 corrector which intrudes a good 15mm or so into the OTA.

[8472]

2 hours ago, Stu said:

Thanks very much. I use it for visual as well so don't want to impact that. Also don't want to slow it down,  think it can stay as is. 

Do you have to remove the secondary mirror?

 

Yes, I did but I had to flock over the cable leading to the back of my secondary to my shed engineered dew heater.

[Bottletopburly]

14 minutes ago, 8472 said:

I didn't know that, David.

 

I've the SW 0.9 corrector which intrudes a good 15mm or so into the OTA.

That’s the one Kev 👍

[+Stu]

I've got a baader CC but I'll definitely check it out. 

[Bottletopburly]

57 minutes ago, Stu said:

I've got a baader CC but I'll definitely check it out. 

I have the baader the mod on the skywatcher was that you had the shoulder machined down on the cc so that it went further into the tube , I use the baader via the m48 thread , I’ve never been quite happy with the baader, I may try the 200pds without the cc just to see what it’s like with the zwo533mc as it is a smaller chip than the dslr, I read somewhere that they had used without with this camera and had come out ok 

[+Stu]

1 hour ago, Bottletopburly said:

had the shoulder machined down

I don't think it'll go any further in. I did see a low profile M48 adapter which would give an extra few mm, not sure it'll be enough though. Also I guess that would affect back focus?

[Bottletopburly]

25 minutes ago, Stu said:

I don't think it'll go any further in. I did see a low profile M48 adapter which would give an extra few mm, not sure it'll be enough though. Also I guess that would affect back focus?

Machine down on the skywatcher only the baader dismantles to use the M48 fitting , yes this alters backfocus to about 57.5mm not great and you can find yourself messing about to get correct distance 

[+Stu]

Thanks for all the advice 😁 Other than that I can't fault the scope. I think I'll just stick with my wonky stars and work on honing my processing skills, rather than mess with the setup.