SharpCap Forums

Hello,
I was curious about trying/using SharpCap Alignment. Preparing a photo lens (2.8/200mm) for piggyback, aligning to telescope (Meade LX90, 8") and viewfinder, attaching my SX Lodestar camera - I in an instand got an image. Started with higher exposer time (10 sec.) later on I could lower it to 4 sec. Step one screenshot appended (the camera image was slightly processed for better impression). Polaris is visible in the image.
In step two 31 stars are recognised and 15 selected. But not solving at all.
I was not able to append the log-file (not as *.log nor *.txt).
What I´m doing wrong? Thank you for help.
Hobbyist

Hi Robin
Here is the log-file appended now. Hope you can isolate my fault. I can not wait to see your results.

Hobbyist

Hi,

your black level threshold and digital gain settings are very high and I expect that this is making it hard for the star detection to work properly. A good starting point for these settings would be 10% and 'Off'.

If that still doesn't help, please grab a couple of frames (save with the snapshot button) of the polar area that are failing to solve and share those.

cheers,

Robin

PS. 2.10 is better at star detection than 2.9, so try that too.

Hi Robin,
thanks for first ideas. I will tray it out as soon as possible (depending on clouds).
The reasons for "unexpected" gain- and black-levels are the poor performance of ASCOM´s driver for SX Lodestar camera. Normally very sensitiv and with good dynamic in SC I need relatively long exposures (I started with lower gain and 20 sec.!). That way the only possibility seemed to higher SC´s digital gain (starting with 1, 2, than 4 and 8) and playing with black level lowering to 30% as well. But I´ll repeat tests in that direction.
Additional I could try to capture some PHD-images (from Lodestar camera) for comparison. And how about to try out the new beta from SC? I read that the algorithms has changed.
In every case it´s my turn now.
Cheers
Hobbyist

Yes, 2.10 is better at picking out faint stars than 2.9. Even with the lodestar a digital gain of 2-4x should be enough and keep the black level down I think. Do remember to capture some frames as you can send them to me for testing (or run them through the test deep sky camera yourself later for experimentation).

cheers,

Robin

Hi Robin,
between 20:00 and 00:00 I had time to try again. Shortly a first report.
My plan was the following:
1. Compare SX Lodestar capture results from PHD2 and SC
2. Changing parameters in SC2.9 as recommended (black level to 10% and gain to "off")
3. Traying SC10.2 beta.
Results:
1. The images from PHD2 with half exposer (2sec) showed comparable number of stars with SC (3.6 sec exposer). PHD2 image without dark image subtraction. Assuming the same ASCOM driver is used in different manner. Hopefully their exists an opportunity to improve lodestar images (sensitivity, native gain) in SC.

2. I changed the parameters carefully (black to 20%, later to 10%, gain first 2x, later "off"). To get sufficient number of stars (15 from 21) final exposer 18.1 sec. Not solving in no case.

3. Using SC10.2 I got just solving with 8 sec exposer (image_4). Turning the telescope 90 deg. Next solving (image_5) shows poor alignment, improved to fair result (image_6 with 30 sec. exposure because of clouds).
Thank you for advise. Now I can continue to improve results.

One trick for more easy adjustment: once my star for moving to the arrows target was Polaris I selected 1sec exposer for live view and after increased to 8 or more seconds for next solving.

cheers,

That looks like it is working just how it should with 2.10 - good news

Robin

Hi all,

last time the clouds interrupted my alignment. Nevertheless I got my best alignment with 2`21” deviation. Yesterday I had the chance to further improve results. Using SC 2.10 beta again with the same lenses (2.8/200), camera (SX Lodestar) and settings: not solving. First playing with settings (gain 2x/ off, black level from 6-16) I got 14...22 stars. Last not least I stopped down the objective from 2.8 to 4.0 (better focus) choosing 18 sec. exposure without result (solving). Unfortunately I can´t append the log-file because using PHD2 for validation my computer crashed (not reaction at all, only possibility to switch off).
I do not see what I can do now. Once more I ask for help.
Cheers,
Hobbyist

Ok, I think you will have to capture some polar frames for me the next time you have trouble - maybe try for a sequence of exposures - one each of

2s, 5s, 10s, 15s, 20s

Then I can have a good look and see what can be worked out for those images. Please capture in PNG format.

cheers,

Robin

I have read your last response in the forum too late. I had finished my next unsuccessful test. Unrespectively the complications because of SC 2.10 beta concerning pro-version I got some solving (after long time) but mostly in one direction and not in 90 degree.
After reading your suggestions I revised the situation and here my conclusion:
Maybe it depends somehow from the camera. Maybe the interlased readout has changed the dark image. Once I have stored them (for different times) I started to analyse the darks. Indeed there seems to be the problem. Look at the (stretched) 10 sec. image from 4-3-2017: Between all the darks their was only one (10,3 sec.) from 11-3-2017 that looks "normal": It´s not hard to imagin what happens if you will use the last image as a "dark". I overlayed the single "good" dark with a no solved by SC2.10 Lodestar-image from 16.3.17: In light red or for small stars in dark red are visible all faults from the chip (from the dark-image). You can see that five of "recognised" for solving stars are red (choosen by mistake). Not solving is predefined. For comparison you can use a star map of the Polaris region.

My question is now: What happens that the most darks are not usable? What can I do, change, try?
Cheers,
Hobbyist.