Initial thoughts on the Astro Tech 8" F4 newtonian....

[Rocket Pooch]

Hi,

Yes result after xNo of months since AstroFest I have actually got out in the garden and used the AstroTech 8" Newtonian.

Just to give some background on the scope, this is sold as an Imaging Newtonian for Digital SLR's and also Large Format CCD's, so hey it should match my QSI853 quite well, I thought.

I will at this point say the scope is about £425, so its not an expensive scope, so I assumed its going to have some issues, its not and never was going to be a £3k Banana scope.

Firstly a couple of things;

1 - You cannot focus on the stars with the supplied extension tubes using a sky-watcher 26mm eye piece, this is awful, I got my scope branded as AltairAstro the extension tube is approx 15mm too short, I will check this out with my other 1.25 and 2" eyepieces to see how they work, but I used a 26mm Skywatcher because I know how many people at my astronomy club have them

2 - The collimation was massively off, if you looked down the tube at the primary it was point well off towards the floor, not great, I would have expected better out of the box

3 - The finder scope mount was so loose the finder scope was moving around, poor assembly and QA

4 - The finder scope is cheap and and crappy, but hey its not a telescope, normal

So I fixed 3 with a screwdriver, 1 this is really bad, I had a long WO extension tube so I could get focus with the eyepiece, but I found collimation difficult because it was not easy to see the whole collimation ring when looking at stars.  2 had a go, needs more effort.  4 ok this is not an issue for me, but it might be if you want an excellent finder.

So there is a real issue with point 1, I had to put a longer extension onto the original crayford, this puts a lot weight and leverage on the craford and it bends at all joints, also because there is a long extension tube its not helping.  I'm going to have a good look at this in the day time, I think the only answer it to replace the focuser with a moonlight.

Lastly I'm a little concerned about the light cone going 2 inches down a 2 inch extension tube then about 2 inches through a Baader corrector and T extension tube to the QSI Chip, with an MPCC in the way, vignetting is obvious.  I think this is a design issue, the focuser is too close to the mirror for DSLR or QSI.

Focusing is not a big issues at F4 but I am concerned about the possibility of it moving due to the focuser.

Anyway 1st light QSI583 10x300 second luminance IR filter only from Cowfold.  You can see the issues with collimation (my fault), possible spacing with the MPCC (it is 55mm back of MPCC to chip, but because the scope is F4 I might need to vary it) and the bend in the image, this is the focuser.  The Joys of F4 Newtonian imaging

So my initial thoughts, the focuser has been moved too far down the OTA, it would have been great to use the focuser without the extension tube to be able to image, I could not focus my QSI with an MPCC with the supplied extension tube or standard focuser.  This scope is primary for DSLR use, I don't think this will change the issue, but I have a EOS300D so I'll check it out.

First light will all the issues M101 10x300 second QSI583

[MarkS]

What a saga!  I commiserate with you on those problems.  However, that first light is certainly showing potential.  If its any consolation, I am still struggling to get my camera aligned correctly on my Tak but I think at last the end is in sight.

I still think that in the long run you won't be satisfied with anything other than a solidly built astrograph with a totally flat focal plane and very well-corrected optics over a large image circle.

Mark

[RobertM]

Sorry to hear of all those problems Chris.  Although it sounds like my Skywatcher is better put together I still had the same issues with eyepieces needing two extension tubes and focuser not up to the job.  The Moonlite I replaced it with is rock solid and holds camera and filter wheel without flex; thoroughly recommended.  You may also want to check whether the tube flexes around the focuser area, that was one reason I didn't consider an Orion.

Though I'm trying to do the cheap astrograph bit too, at the end of the day I think Mark has a very valid point.

The image shows a lot of promise; should be really good when you get the collimation sorted.

Robert

PS. It's good to see you imaging again.

[Fay]

I think the image shows a lot of promise too. The galaxy and background looks good. I must get my 8" out for a practice, now we seem to be getting a run of good weather!!!!!!!!!!!!!!!!!!

I have setup for tonight, to see if the Atik/ filter wheel will focus ok with the Leitz, not a lot of backfocus. Will publish my problems tomorrow!!!!!!

[Rocket Pooch]

Ok I have worked out the issue with needing the extension tube for imaging, the primary was too far forward.  It is meant to be clear tomorrow and fantastic at the weekend, but I'm going to put this one down tomorrow and try the OAG out I bought in whenever that was as well.  Set it up statically today and all seems ok, if it works this is the complete list of cables I'll be imaging with in future.

2xUSB one for guider one for imager
3x12v one mount, one main camera, one dew heater
1xserial cable to use the mount

6, thats 6 cables I remember a couple of years ago I had 11.

Anyway lets see of the OAG will work, focusing it is going to be a laugh, but when I know the exact focus point it will work on all the imaging scopes without needing to be moved.