Thoughts from Starlight Cascade

After a dewy FallNStars star party weekend it was time to go back and start working on making work all of the various dew heating bits and pieces we have laying around.

I found a bag of heaters, and a mouse nest. Got rid of the mouse nest and discovered a hole in the middle of the 40″ heater, mainly the felt
cover with a few nibbles on the heater as well. And on another 6″ heater, the end velcro strap was totally gone.

So.. All of these items are now stored inside a plastic bin. Yes, I know this will not stop the mouse built it will slow him down.. and I will be
able to see inside and if I see him, wave a goodbye! Will repair these two in the next few days.

So, a kendrick 40″ strap will work on a 12″ diameter telescope (C=D*Pi) D=C/Pi=40/3.14 = 12.7″

The 19″ strap (19/3.14=6) is good for a 6″ diameter telescope and the 6″ is good (6/3.14=1.9) for a 1.25″ eyepiece.

Resistance wise, the 6″=52 ohms, the 19″ is 9.4 ohms and the 40″ is 5.2 ohms

V=IR, Power=IV= V^2/R so

the 6″ strap at 52 ohms at 12 vdc gives 12^2/52=144/52= 2.77 watts

the 19″ strap at 9.4 ohms at 12vdc gives 12^2/9.4=144/9.4= 15.3 watts

the 40″ strap at 5.2 ohms at 12vdc gives 12^2/5.2=144/5.2 = 27.7 watts

It’s been a week since our last astronomical imaging session. Perhaps this satellite image of CLOUD helps to explain why. That and the high humidity leaves transparency very low.

On the night of Thursday 2018 August 30th EDT, or Friday 2018 Aug 31 UT, I went out in the intermittent cloud and heavy dew to run a test of the Serenity Imaging Platform with a variety of barlow lenses.
Seeing was poor, transparency was poor, no mosquitos! but dew was falling even as the sun was setting.
Jupiter was still visible this early evening so I pointed and aligned on it and did a regular image run of 30 seconds with firecapture align on.

This is the result, worse than past nights but some surface detail is there.
This image was firecapture flipY (ie one inversion of the Y axis, so north should be up). Exposure time was up a lot due to the cloud and poor transparency.

Pointed over to Saturn, near zenith but a lot of intermittent cloud.
There were three barlows: a x2 Antares (lower cost), a x2 Celestron (a little more) and a x3 televue (a lot more).
The three images below are 30 second imaging runs, the first two at 100ms exposures and roughly 150 frames, the last at 190ms and roughly 80 frames. They were then processed and stacked using the best 25% of the frames.
The absolute low number of frames stacked is why they look so noisy. Only 40 frames on the first two and 20 on the last.
Focus is far more critical and is far worse in these images. Surface detail is lacking after registax wavelet processing.
Each barlow lens is mechanically different, with the lens mounted at different distances, requiring a coarse focus adjustment when switching from one to the other.

x2 Antares

x2 celestron

x3 televue

No dew shields on the corrector plate of the telrad yet… those are still coming. No dew heater power yet either.
Targets generally move out of the barlow Field of View when I step anywhere inside or move around inside the imaging platform. I was hoping the heavy construction (deck blocks on gravel on limestone rock, 2×8 joists, 12″ on centre, 7/16 OSB floor) would minimize or eliminate it.

Results:

No real quality difference was seen between the barlows, as the images were too poor to judge. Will have to repeat in better seeing and transparency.

Serenity Imaging Day 4
Still commissioning. Another hour last night from when the stars came out until the fog and dew stopped the work.
The 90 degree diagonal came off the scope. Why?
It is good to have when using an eyepiece (less bending over wayyyy to low) but for imaging it is better off off.
1) It extends the optical path and longer is not necessarily better.
2) You gain photons by eliminating the loss caused by the optical mirror surface, in general maybe a 10% gain.
3) You eliminate another optical flip in the image (from bouncing off a mirror)
4) This one is huge and I never thought of it until the diagonal came off… eliminating another source of dust and dirt in the image from the dust and dirt on the mirror. Holy cow Batman! It was dirty!

Schmidt Cassegrain reflector will produce an image that is upside down (flipY in firecapture parlance) when used without a diagonal. When a diagonal is used the image will be corrected right side up, but backwards from left to right (flipX in firecapture parlance)
Will confirm this with the moon next session.

Walking out to the Observatory was bad last night with high temperatures and high humidity… ground fog to a large degree and lots of dew.
Turned on the scope from the park position, went to Mars, then back and forth trying to achieve a new coarse focus of the primary mirror and actually having mars in the field of view of the camera. Removing the diagonal changed the coarse focus. After a few minutes, Mars was in the FOV and was coarsely focussed.
Fine microfocusing was next then some sample images, 30 seconds without firecapture alignment, 30 seconds with firecapture alignment and 60 seconds with alignment.

Goto Saturn next, still near its transit point almost due south. It was not quite in the FOV but was within the 1/2 degree telrad inner circle. A little bit of searching found it and four more images were taken: 30, 30, 60, and 90 seconds. By this time the telrad was dewed over, the primary mirror (still without a heater or shield) was dewing and it was time to go in.

So tonights session was: no diagonal, zwo asi120mc camera, no barlow, no focal reducer, no dew shield, no dew heater.
Oh! Here are the three mars images and the three saturn images:

Mars was the best 10% of the frames taken used to stack as seeing was poor, transparency was poor and Mars was still low in the Southeast. The south Polar Cap is showing as well as some dark features in the southern hemisphere.

30 sec no align

30 sec with align

60 sec with align

Saturn was the best 50% and only the 90 second image run is shown here. The Cassini division is finally showing!