Will this Guide ??

[PeterN]

Been playing with an old 400 mm Sigma telephoto lens today and works fine with the QHY5 Guide Cam but wondered if it will make a Guide scope. Its an f5.6 400mm with an objective of 70mm. You can find these cheap in second hand camera shops. This one is a Minolta MD mount.

Focus is a bit course but it images OK but had to stop it down to f22 to get a good image in day light.

Just need a cloud free night to try it out.

What do you think. Should it be OK.

The mount is a cheap ball socket off a lidel £2 tripod. No very solid and will need replacing with a solid bar if the lens works.

Thanks,

Peter.

[steppenwolf]

No reason why it shouldn't be useful as a guide 'scope, after all, many people (including me) us the little ST80 as a guide 'scope and this too has a 400mm focal length.

[Kaptain Klevtsov]

It should even work with a webcam Peter. I use an ancient Russian 500mm f/8 Tele lens and Mk1 Toucam for guiding a lot. Works for me.

Like you said, you'll have to stiffen it all up a bit to stop the guide 'scope sagging, but that's mechanical.

Good luck with it.

Kaptain Klevtsov

[centroid]

Yep, I agree with Steve & KK.

As Steve said, he successfully uses a 400mm ST80 as a guide scope, and so did I for a while.

Let us know how it works out for you.

Dave

[PeterN]

Well I dug out an old set of rings and mounted them on some equipment bar on the 80ED and used the Guide port on the QHY5 direct into the ST4 port on the AWR drive box and run PHD. PHD calibrated and away it went. Grand job. Tried it on M13 as thats an easy one and hoped to go on to M101 but the clouds rolled in after about 30 mins and it was pack it all up time. The QHY5 is a great little camera I was using exp. of 2 seconds and had no problems. Used the Atik 16IC as the main Cam.

Peter.

[steppenwolf]

That looks great and should work well.

I notice that you are using the main camera mounted on a diagonal - have you considered mounting it in line with the main 'scope as this would be more 'rigid' which would help with the stability of the whole imaging system? You would, of course, require an extension tube to make up the loss of 'length' in the system but you would be removing one reflection and helping with 'flexure' at the same time - might even make things easier to balance as currently, the camera is on one side of the centre line. The following is an image of my system with the extension tube in place:-

[PeterN]

Hi Steve,

Many thanks for the info. I have used it in line but it was one of those nights when you get some thing working and give it ago. The diagonal hopefully won't be used when I get some more clear nights.I'll also remember to remove the moon filter next time as well !!!

I like that set up you have. looks like you have it all installed in a dome as well.

Cheers,

Peter

[steppenwolf]

I'll also remember to remove the moon filter next time as well !!!

:lol:

I like that set up you have. looks like you have it all installed in a dome as well.

Yes, I have - one of my better investments!

[iancandler]

Please tell me thats not a pentax fit sigma 400mm..especially dont tell me its the APO macro version or autofocus..

[MartinB]

That set up looks the business Peter.

[PeterN]

Hi Ian,

Sorry for the delay in answer. No it's an Minolta MD mount Sigma 400. I tried to trade it in when I wanted a new lens and no one would give me more than a fiver for it so I use it for guiding. I,ve seen then in secondhand shops as low as £15 so it makes a cheap guide scope.

Peter

[iancandler]

Sadly the minolta ones stayed pretty cheap for a while, but I think they fit the new sony DSLR's so should go up again.

The only problem with them is the non apo versions are a little soft, but it should work fine as a little guide scope.