20170531 Home@Walnut testing of the 328

I did the final modification by introducing a short back tube of 2" diameter, it was fitted exactly from the rear lens of the 328 and the 1.25" adapter.  So, if that could not eliminate the internal reflection, it is then the intrinsic issue of the 328 optical chain, nothing to do with my modification. Therefore, I call it the final modification.

That tube looked really dark.....

The first test was conducted visually with a Canon 2x extender before a 1.25"diagonal, plus a 20mm eyepiece.  The resultant focal length should lie between 600mm to 900mm.  That is effective magnification of 30x to 45x. 

The moon is very contrasty and sharp!  Free of any false color, so I am encouraged.

Here is the first shot:

It seems okay, but the experienced eyes will know there is something wrong.   Adding a 5x powermate confirms that it sucks:

The contrast is very low, a signature of internal reflection.

Later on the same night, when Jupiter reached my window, I tested and confirmed that internal reflection was reduced, but it still exists,virtually no detail could be detected.

That modified 328 should be reserved only for imaging of DSOs.

20170530 Dragon Boat Festival Imaging

Again, I went back to that playground last night.

No wind tonight, better seeing... I guess around 6/10.

I setup the Nexstar in the wrong direction, I thought it will work, but then it fails to track properly, in short, it tracked with exactly opposite direction.  I believe two points alignment would do, but since I do only solar system alignment, so it won't know unless the initial position is fixed.

At first I guess there might be something wrong, and I redo the alignment but things kept on wrong.  Finally, I reversed the mounting direction of the tube, and thing got right by then.

There were no visible bright star on the sky due to the heavy light pollution, so I don't have any good target for collimation, I couldn't use high power diffraction pattern on dim stars.  So I just randomly picked a star, defocus a bit and collimate briefly with it.

I setup my scope where there were many flying insects, and my head was buried in the plants during alignment, so bad.  So I really have no mood on doing good collimation or focusing.

Moon at prime focus, 1319 UT

Jupiter with 3x barlows, 1330 UT, 150% resized

Jupiter at 1330 and 1332 UT, C5 with 3x:-

Nexstar mount, C5, 3x GSO barlows, ASI 120mc camera with my trusty and cheapy Teclast tablet.

20170529 Short imaging session

Quite windy these days, so I brought only the Ranger for this fun imaging session.

The moon is setting, so this is just a prime focus shot, taken at 1222 UT.

And we have a 2x shot, of the Jupiter, taken at 1228 UT.

Finally, push up to 5x, i.e. 2400mm focal length, taken at 1236 UT.

Using the Ranger is much easier for this Nexstar mount.

Further testing of the Canon FD 300mm f2.8L in scope mode

I have done some work on the internal reflection issue before, but no testing since then.  Today I have a cloudy afternoon and thus it is a good chance to test it out with a EOS 1.25"adapter.

First test was conducted with a diagonal. Yes, it won't focus unless I add a barlow in front of the diagonal or a 2x extender, 2x extender seems more elegant.  In short, it's sharp with my 20mm eyepiece.  I expect around 50x with this configuration.

Pulling the diagonal off should be a better test, it's even sharper since the effective focal length could go down to 300mm!  I took the plunge to use it at 3000mm, yes, 3000mm by using a 2x extender plus a 5x Powermate, and so we have 150x and it remains very sharp and contrasty, too.

I guess I should try it out with the moon or the planets, probably with a camera.  I hope it could replace my C5 eventually, if it is also good as a 4" refractor.

 --

After writing the above short report, I pulled it out again to try higher.

First test was with 2x extender with a TMB 4mm, so we have 150x again.  Sharp and no image break down.

And then I added a 2x barlows in the same setup, so we have 300x!  Floaters come in but again no image break down, focusing was easy.

I'm quite confident now.