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C8 focusing question

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19 years 1 month ago #12253 by Bill_H
Replied by Bill_H on topic Re: C8 focusing question
Can you get something like this Dave, it's one of my next purchases: www.telescopehouse.co.uk/page.aspx?theLa...1204A&action=lnk
It probably won't help with remote focusing, or mirror flop, but like Dave L I'm tending to steer clear of auto-focusers as something like the above will probably help with a good feel for accurate focusing.

Astronomers do it with the lights off.

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19 years 1 month ago #12254 by michaeloconnell
Replied by michaeloconnell on topic Re: C8 focusing question
I have one of those Bill on my LX90. In theory it's a great idea, however in practice you're better off just focusing by eye I reckon. However, mabey I just haven't taken full advantage of it.
What I find excellent for foucsing is my Borg 1.25" non-rotating helical focuser. When it comes to high-power views of the planets or especially for webcaming, this really is the business. I posted a mini-review of it here:
tinyurl.com/8u2n9

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  • dmcdona
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19 years 1 month ago #12255 by dmcdona
Replied by dmcdona on topic Re: C8 focusing question
Dave L - I understand where you are coming from but I'll be using one of the CCD packages which, by measurement of the image, enables precise focusing.

Up 'til now, I've been manually focusing and if you've seen my images, I'm sure you'd agree that I'm doing a pretty good job. However, I need to do better with the work I'm proposing to do.

And as you mention the mount, its clear that the 1200 is so good that it makes everything else out-of-wack. For example, orthogonality of the optical axis to the DEC axis is a major issue now - I'd never considered it before because of the fork mount. Polar alignment is critical but I'm getting better at this.

And now that I have the ability to point at the fainter objects I want to study, focusing is now an issue (as well as collimation of course). If I can't achieve good focus (for CCD work) then the fainter objects just disappear.

For example, I usually get my focus by starting on one of the Gallilean moons then switching to a slightly dimmer star, then checking back on Jupiter. So far I've been successful at this. But if you notice that when you throw your scope out of focus, you may still see Jupiter but the moons are gone.

Of course, because of the mirror flop anyway, precise focus is always going to be a continuing requirements as the scope moves. And I can't stand at the scope and just focus all night long!

As I said in my original post, I may go for the Borg helical focuser a la Micheal O'C, but that would be an interim solution I guess. Automated focusing is where I need to be.

It may be that I'll just have to put up for now until I get a new OTA that doesn't suffer from mirror flop....

Bill - I dunno if the focuser you refer to will fit the Celestron... I assume it won't. But there may be models out there that do. Time to do some research...

Thanks for the posts folks - much appreciated. Keep them coming!

Cheers

Dave McD

ps - does anyone know a good daylight method for modifying orthogonality?

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19 years 1 month ago #12256 by Bill_H
Replied by Bill_H on topic Re: C8 focusing question

I have one of those Bill on my LX90. In theory it's a great idea, however in practice you're better off just focusing by eye I reckon. However, mabey I just haven't taken full advantage of it.
What I find excellent for foucsing is my Borg 1.25" non-rotating helical focuser. When it comes to high-power views of the planets or especially for webcaming, this really is the business. I posted a mini-review of it here:
tinyurl.com/8u2n9

Ooh! Michael, just when I think I've sussed things, along comes someone with a beter idea :?
Looks to me to be the business, much better than the focusing knob.
Pardon my stupidity, but just want to be clear. This unit fits into the eyepiece holder, then the eypiece/ccd fits into that?
I think this might be the focusing aid I've been looking for.
Thanks Michael.
Bill H.

Astronomers do it with the lights off.

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19 years 1 month ago #12258 by michaeloconnell
Replied by michaeloconnell on topic Re: C8 focusing question

Pardon my stupidity, but just want to be clear. This unit fits into the eyepiece holder, then the eypiece/ccd fits into that?


Bill,
That's a fair enough question as it seems a little strange to understand at first. This focuser is designed for 1.25" eyepieces to fit into. It's part 7315. You need the adapter 7316 to screw into the bottom of it for it to fit into a 1.25" diagional. The 7316 adapter is the bottom piece with "31.6" written on it as shown in my photo. This 7316 adapter screws into the bottom of the 7315 focuser.
Overall, the focuser has 10mm of travel and is extremely well made. You can easily get 0.05mm focus as it's really smooth with no slippage/backlash at all. The only thing better than it would be a 2" version. I've often though about getting one but they are very big and expensive. However, they would be the bees-knees. Hopefully I've explained it a little more clearly.

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19 years 1 month ago #12259 by Bill_H
Replied by Bill_H on topic Re: C8 focusing question
You have explained perfectly Michael. looks like that has now replaced the other on my "To buy list".
by the way, Lesley wants a word with you :lol:
Bill H.

Astronomers do it with the lights off.

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