QHY5v - solar imaging

[obscura]

This is just not working for me. Have the instruction manual but its not that explicit. I appear to get a clear solar edge with the two sliders but spots in the disc are non existant. Running focus causes some big black blobs to appear. Have tried exposure from 1ms onwards and gain is limited in use. Have played with the two sliders but although they make a difference, no spots. Seems its all over exposed.

I must assume I am missing something, but what?

QHY5v tried at prime extended by 2" and on the diagonal

[jgs001]

I had the same issue, way too over exposed. I had to use a 2x barlow on my 80ed with the baader film to get the scope to f/15 to be able to get the exposure low enough to capture the spots.

[obscura]

Hi John. Thankyou for your quick response. I gave up come lunchtime after 2-3 hours of trials. The sun has now disappeared for the day but if all is clear tomorrow, I'll give that a go. Using a Barlow to reduce f stop never occurred to me.

I'll advise on progress.

Best Regards

Brian

[obscura]

The saga continues. I can now see spots but there are many black blobs which I have no idea as to what they are. The optics are clean. Cannot adjust them out without losing the spots. Help!! Do I have a QHY5v problem? I did rotate the camera and the blobs stayed as thet were.

sunqhy5v020611_00004.BMP

[riklaunim]

You need to clean the sensor cover... I have to do that every imaging to get rid all of them. They are invisible to the eye and require using for example Baader clean wonder + cotton bud. Spray the bud, clean gently the sensor front glass, then start cleaning with the dry side and blow some air on it to vaporize all of the Baader liquid (and to blow away cotton fibres).

[obscura]

Looked clean but I take your point. One thing though, I rotated the camera and the blobs did not move with turning. Would not that point the finger elsewhere? Would a 10% distlled water and iso propyl alcohol do the trick? I have them. I have dismantled and checked and found some dust specs on the diagonal mirror, now removed.

Best Regards

Brian

[riklaunim]

They won't move as they are on the front glass of the sensor. Those are very small dust particles that can't be seen or blown by air easily. That alcohol will do the trick. Water isn't needed or good as it won't evaporate instantly.

[obscura]

The sunspots moved on rotation of the camera in the scope and the blobs didn't. Don't quite understand as the glass on the sensor would rotate too? However, the clouds are beginning to roll over so I can spend time cleaning this afternoon.

many thanks for your help and advice.

Best Regards

Brian

[Rossco72]

You might have small dust bunnies on your main optics, mirror if you are using one, barlow if you are using one, filter if you are using one, camera sensor cover or alll of the above.

Larger spots usually mean closer to the sensor so probably not your main objective but diagonal, barlow or camera could be the culprit.

[obscura]

Thanks Stuart. Have gone through the barlow, diagonal and sensor surface and gently cleaned with q tip and breath. Did an off line check with camera plugged into laptop only and did not find any blobs. All the kit is about three months old so they shouldn't be in too bad state. The only other glass in the optic chain is the scope's objective and that looks fine.

Maybe, just maybe all will be well tomorrow, barring cloud cover.

Cheers

Brian

[Rossco72]

specks of dust on the objective would be just a few pixels across, if it's big spots, probably looking out of focus, then its definately something closer to the sensor.

[riklaunim]

The sensor front window

[obscura]

Hi and thanks to all. Aftter yesterday's optic cleanup with a gently used q tip and a breath, sensor, barlow were cleaned with the diagonal getting a mere blow.

The results seen this morning was a single blob on edge of frame which was of no consequence. Managed to take in excess of a hundred frames though couldn't do much about shimmer. Hopefully, post process with photoshop will improve an image or two.

Would Autumn/Winter be better for solar imaging?

Best Regards

Brian

[riklaunim]

Dusk and dawn are good for solar imaging when the air is at constant T. In general it's hard to make good solar images (due to that air turbulence). Some filters can help (Solar Continuum for example, or adapted industry filters for other "bands" like TiO 706nm for wedges, ~590nm yellow shortpass with Astrosolar on D1, D2, D3 Fraunhofer lines etc.)

For solar imaging my scope looks like so:

The thermoisolating foam prevents the OAT from heating up = which would cause air currents inside and spoil the images.

[obscura]

Interesting. Thus a combination of air thermals and currents in the OTA. Dusk and dawn are very awkward here as rooftops get in the way - right now I have to wait until near 9 in the morning before the sun appears over the tops. i may stand a better chance in evening though its not much better in suburban Basingstoke.

Your thermoisolating foam. Is it made for the job or just an ordinary foam?

[riklaunim]

Ordinary, bought in supermarket in the tourism department. I've cut it a bit to fit the OTA on the mount, and it does work nicely (after ~2h in the Sun it didn't got noticably warmer).

[obscura]

I'll look into that. Many thanks.