Which OAG and Which Guide Cam?

[bartman (Bart)]

I'm looking at getting an OAG for my setup/s.
Reading/ looking at the posts on IIS, I cant seem to get a definitive answer.
So here are a couple of questions the community might/could help me in the right direction.....

1:Recommendation for an OAG for both my 80 SW and 254 SW. The 254 has a moonlight focuser.

2:What is more useful to use on the OAG? A webcam with PHD( or similar software) OR a dedicated guide cam such as QHY - Orion Starshoot autoguider
Or should I go for an Orion Starshoot solitaire?.

To be honest, I dont want to spend $700 ( + $ on the OAG) on the solitaire .

I still have training wheels attached to my scope!!!!
I have a webcam attached to a finderscope that works ok ish with PHD, but I can only get very bright stars to work.And even then not sure if its doing the right thing!

From reading the posts, I need some more inward travel when using OAG's, especially on newts ? .... ( guess that is a third question)

The reason for my questions is that I am into the astrophotography side of astronomy.

I realise there is a lot to it ,but I still have three training wheels.....
Slowly, But Surely each training wheel will come off one by one....in time.

Bartman

[TheDecepticon]

I don't know what the others are going to say, but I would go with a dedicated guide scope and any of the guide cameras you mentioned should be ok. With an OAG, your are going to perhaps face framing issues to get a suitable star on the guider prism, and with a guide scope set up, you will need to overcome differential flexure problems. Also, I believe focus travel on the 254 will be an issue, preventing an OAG being used. OAG user please jump in here.

Nothing is cut and dried here, there will alwys be those that are for and against. You need to decide which way you want to go and whether it is in your budget.

Check out this guide scope package for reference.

https://www.bintelshop.com.au/Images/Stock/8162X.jpg

Cheers!

[pmrid (Peter)]

1st thing to note is that an OAG does use up some of your back-focus so before you go down that road, be aware of how much you have on your setup. Different brands have different back-focus demands.
The brands I have used are Lumicon, Celestron Radial and Orion Deluxe. Atik also make one that look good and seems to have a very small backfocus. Of the 3 I have used, the first I eliminate is the Lumicon - too much backfocus and no radial capability. The other 2 both have radial capability but the Celestron one is primarily designed for an SCT (I modd'd it to suit a newtonian but it wasn't a great success) and the last OAG standing is the Orion but it looks to me as though the Atik is worth a look as well.
The webcam should be dedicated if only to get an on-board ST4 port to plug straight into your mount - fewer cables back to the computer = less clutter. The choices are basically between Orion and QHY5 - I use the latter and have found them excellent value and performers. I was turned off the Orion version because of cost but uderstand they are essentially the same camera in different livery anyway.
I am not using an OAG at the moment having found them just a bit too fiddly. I prefer the flexibility of a stand-alone guide scope.
Hope that helps.
Peter.

[mldee (Mike)]

I'm no expert, but I'll add my experiences for your evaluation. I've done no OAG, just the guide scope route. I started with 80mm f6 SW guidescope and QHY5, piggy backed and using PHD+EQMOD. Worked well enough for a newbie.

I eventually thought it was all a bit big, clumsy and flexy, so then went the finderguider route with a DSI II mono hanging off the back. Small scope = light weight = less flex, and the DSI has a very sensitive Sony HAD chip, so always tons of stars. Again, PHD+EQmod. I have it mounted in a side by side arrangement so it doesn't need to get disturbed when I change out scopes, from my Newt to SCT to refractor. It's always there ready to guide.

A small benefit is the low cost finderscope allows one to put more $$'s into the camera, as used DSI's are still about QHY5 price. It's a bit more of a DIY'y approach, but compact and functional. Of course, YMMV.

[bmitchell82 (Brendan)]

The OAG wont work with your newt, as it is a canon 40d has if that 5mm back focus to spare. the other thing that some ar'nt mentioning, is that a OAG+guide cam is going to weigh your focuser down. so what was going to be a OAG+guide cam will turn into a 3-500 dollar focuser as well.

I know for a fact that the SW focuser isn't really good enough for holding a 500g DSLR let alone anything else.

For the 10" use a 80mm ED refractor that doubles as a wide field. for the ED put a finder guider on it and it will be brilliant!

If you defiantly want to head down the OAG then you'll have to do some decent modifications to your newt to get A. the in focus, B. Stability of focuser increase to a minimum of 2.5" if not 3" focuser which leads to. C. increase the size of your secondary to accommodate for the mirror moving up the tube. It can be done but you have to think about a few things first.

Currently im working towards OAG, but I will most likely just hit AO straight up, as starlight does a great little set up for it. Its not cheap, but there's definite benefits to it. Hope that gives you a bit of a understanding.

[marki]

TS optics make a nice thin (9mm) and light OAG which may or may not work with your setup. It would be an interesting experiment in any case. You can get one from here.

http://apmamerica.com/index.php?main...roducts_id=105

I have several OAG's including the TS OAG 9 which I have used in refractors and SCT scopes. When all the odds fall in your favour they are great, but in most circumstances they are a right pain in the behind. Framing objects to suit your purposes and finding a suitable guide star can be more of a challenge then actually getting the mount and camera to do their stuff. Luv em and hate em at the same time.

Mark

[bartman (Bart)]

Thank You all!!!
Some stuff to think about.....
Mark I do like that thin profile OAG! A little expensive....But how does one attache it to the scope? Looking at the pic, the three thumbscrews would do that but it looks like the prism would get in the way. It there and adapter tube for that with the prism bit cut out?

Once again thank you and I'll post later tell of the road i'll go
bartman

[mithrandir (Andrew)]

Originally Posted by marki

I have several OAG's including the TS OAG 9 which I have used in refractors and SCT scopes.

http://apmamerica.com/index.php?main...acturers_id=18

or

http://www.teleskop-express.de/shop/...-fuer-CCD.html

How do you work out which adapters you need? There are so many bits to pick from.

[marki]

Originally Posted by mithrandir

http://apmamerica.com/index.php?main...acturers_id=18

or

http://www.teleskop-express.de/shop/...-fuer-CCD.html

How do you work out which adapters you need? There are so many bits to pick from.

Bart the three thumb screws only lock the inserts to the main body (see below).

There are only really two options Andrew. One side is solid with 48mm thread and the other side is an insert held in place by the three thumbscrews. For the camera side you either buy the T thread or 48mm thread inserts (same as 50mm filters and most 2" nose pieces with metric threads). For the scope side you will need a 2" nose piece with 48mm threads ( I use one from a 2" WO diagonal). APM only supply the T thread version. You will have to buy the 48mm insert from the teleskop service (your second link) at least thats where I got mine from. Please note that these OAG's whilst being incredibly thin and light offer little room to rotate the prism (about 5 mm at best) and are really restrictive when it comes to framing (no guide star = no auto guiding). This means you have to rotate the entire camera to find a suitable star unless you are really really lucky. Also remember that it cannot go any old place in the imaging train. It must be set so the guide camera chip is at roughly the same distance as the camera chip from the pickoff prism if you want to have any chance of bringing both cameras to focus at the same point (there is about 10mm adjustment). I posted a few pics of my setup a while ago, will find the thread.

Here it is.

http://www.iceinspace.com.au/forum/s...t=58016&page=2

Mark