Carbon tube 8" F4 astro graph (I hope)

[Rocket Pooch]

Right, its done and its on the mount for a trial, I have not flocked the tube yet or cleaned the mirror, or sorted out how dirty it is (house move).

But the guide and finder scope are on it, it even comes to focus with plenty of in focus for the F3.6 or F2.8 reducer.

I'm going to give it a 1st light tonigh and see how its goes.

Nothing like making your own kit, well specking and assembling more like.

Spec 8" F4 newt, steel track focuser, 9 point mirror cell holder, 8mm thick carbon tube, 75mm secondary.  Total build cost approx < £400.


DSCN4265 by chrissuddell, on Flickr


DSCN4263 by chrissuddell, on Flickr


DSCN4262 by chrissuddell, on Flickr


DSCN4261 by chrissuddell, on Flickr


DSCN4260 by chrissuddell, on Flickr

[Jim]

Looks the business Chris, will be interested to see the results. You taking orders?

[MarkS]

It certainly looks solidly built, Chris.

I'm looking forward to seeing how it performs.

You'll need to stay awake beyond 8pm though!!

Mark

[Rocket Pooch]

Its out there doing its thing, collimation out a bit, no diffraction spikes on a mag 4 star with the QSI

Lets see what a frame looks like

[Rocket Pooch]

Right I have seen this before with MPCC's one corner is not 100% but the frame looks ok, so a little crop will work, the focus is 1.5" back from the stop therefore there is plento of room for other coma correctors, I will get a skywatcher one.  The secondary is a lot better placed than on the old astro tech virtually no vignetting now

All good so far, I'll grab a few frames do some flats and call it a night soon.

[Rocket Pooch]

Ok, I checked the MPCC it is sitting quite flat so I re-colimated and re-did 6x5 mins on M101, no flats (light leak from laptop, doh!).  Also I did 6x2 mins on Alkaid, on a normal newt the diffraction spikes would take over the whiole frame.

Click on the images to get to the full size versions.

Chris


M101-6-5-min-Sig by chrissuddell, on Flickr


Alkaid by chrissuddell, on Flickr

[MarkS]

Looking very good.

Star shapes are good everywhere except just little squiffy to the top left.

This is only the first night  so you must be well pleased with this and you have plenty of time to make further slight adjustments - so things can only get better!

[JohnP]

Looking very good.. like you say collimation a tad off & star shapes a little iffy top left but loads of photon's... Liking the curvy diffraction spikes (not many either for such a bright star) - Looks like a winner once you sort out the minor adjustments.

John

[Rocket Pooch]

Robert, Julian and any other DIY nuts, have a read about the corrector this guy is using, it reduces by .9, this is the one I'm going to get for this scope, then it will stay here in the observatory waiting for the summer, 8" F3.6 with a QSI, should be interesting.  http://stargazerslounge.com/imaging-deep-sky/159089-skywatcher-quattro-10cf-first-light.html

Couple of things I did learn/ forget, 1 - the opend tube design picks up any stray light, doh! laptop LED's illuminating the scope from below, 2 - my flat panel is too bright for this scope, so I'll need a ND sheet.  Making the flat was not easy and I won't be using it, but you can see the secondary is about bang on in the middle.

Final collimation was done with the camera in place, with an images and a computer drawn circle, when the out of focus circle was band on in the middle of the field of view and circular against the draw circle I was happy, this is why I think the stars are out because of the MPCC or pinching.


Flat Newt by chrissuddell, on Flickr

[Fay]

looking very good Chris!!

[RobertM]

I'm really looking forward to seeing the first non test image.

[Rocket Pooch]

Well the issue has to be the MPCC, I have found this image with a different scope, different camera and same corrector, same issue;


IMG_0592 by chrissuddell, on Flickr

[MarkS]

Your MPCC is doing a pretty good job but to get perfection you'll probably need a Wynne Corrector.

Mark

[Rocket Pooch]

Hi Mark,

Na I think I can fix this and the stray light as well, then I'll get the ASA 2" corrector will allow me to go from F4 to F2.8 with the same scope.  Or F6 with the correct 2" barlow.

Chris