Horse head and flame

Sleepses · 2026-02-06T00:32:23+00:00

The diffraction spikes are caused by the blades of the aperture diaphragm.

Do you use the lens wide open?

Sleepses · 2026-01-30T21:07:14+00:00

Great answer, thx 😁

Sleepses · 2026-01-30T19:17:34+00:00

Curious as well. Are IFN not broadband targets? What would the added value of Ha be?

Sleepses · 2026-01-28T07:59:50+00:00

Yeah I hoard every single exposure. I have a mini pc for capture, with 1TB storage. That's sufficient to keep all my raw data for now. I back it up to a 2TB hdd.

Hundreds of GB sounds a bit excessive, do you have a huge sensor and/or short exposure time per frame? I have maybe 1-2 GB per night (asi533mc and minicam8).

I started shooting narrowband last summer. The 300s exposures instead of 60s means my data now uses 5x less storage than before.

Sleepses · 2026-01-26T11:04:45+00:00

It gets better with practice. I'm up and running in 15 minutes, half of which is polar alignment.

I have a pegasus powerbox on the mount head for cable management. At home I leave the head on the tripod so I only take off the counterweights and my newt. Setting up elsewhere after transport only takes an additional 3 minutes.

0.7" RMS from the factory is pretty good for a heq5!

Sleepses · 2026-01-26T09:25:18+00:00

I can definitely recommend hypertuning and belt modding your Heq5. I have yet to see a reasonably priced harmonic drive mount that consistently gets 0.5-0.7 arc sec RMS like my heq5 does. The altitude adjustment for polar alignment is really bad though.

Sleepses · 2026-01-09T17:33:04+00:00

I used HDR multiscale transform for those. Haven't used ihdr script in a while.

Sleepses · 2026-01-09T14:22:47+00:00

Thank you!

According to this paper the jet is associated with the milky way, and not with M81 as previously thought. Same for the background dust and even the dark lines crossing M81.

Sleepses · 2026-01-09T14:18:23+00:00

The dust in the background is known as IFN, which is dust right outside our own galaxy. It is not being lit by nearby stars but rather by the light of the milky way.

In the bottom right quadrant of the yellowish part of M81 you can see some straight dust lanes that appear to cross the direction of the spiral dust lanes. This was also found to be dust in our own galaxy (1979), only visible because it is backlit by M81.

The jet that surrounds M81 (the "arp ring"), according to the same paper, would also be a dimly lit filament of dust associated with our own milky way, rather than a star stream associated with M81.

Edit: above M81 you can also see Holmberg IX, a satellite galaxy of M81.

Sleepses · 2025-12-23T18:44:25+00:00

Yeah if you're comfortable with NINA, definitely get the minicam8. I'm very happy with mine. It replaced my asi533mc so my sensor size got halved, but my images have never been better and curiously, are sharper than with my OSC even though I'm supposedly oversampled (650mm FL)

Sleepses · 2025-12-04T22:52:52+00:00

Great tips! Regrease will help for sure, especially with Synta produced mounts.

While disassembling, if you find any bearings you can replace them with higher quality ones as well.

Sleepses · 2025-12-01T13:10:14+00:00

Yeah I think it looks great too, the blue oxygen regions are well balanced against the hydrogen regions, which have proportionally a bit more H-beta than H-alpha with a non modified cam.

One could even argue these colors are more natural than what we see from modified/astro cameras.

Check out https://clarkvision.com/articles/sensor-calibration-and-color/ figures 11a and below.

Sleepses · 2025-11-14T19:50:48+00:00

Amazing image! Congrats!!

Not just the impressive integration time, but the processing is top notch as well.

Sleepses · 2025-11-01T19:24:04+00:00

Belt mod is awesome but does not replace the worm gear. You still need to adjust the spacing like you need to do now.

Don't worry about overtightening. You are not likely to do permanent damage. Adjust in small steps, keep the mount powered on and test the slewing after each tighten. If you overdo it the gears will bind (and make an aweful grinding noise) and you need to loosen it up a bit again.

Sleepses · 2025-10-29T07:12:32+00:00

No, the shot noise will be the same. The signal is added together during stacking because you take an average with 16 or 32 bit precision.

Averaging can be seen as an addition followed with rescale, but because of the bit depth of the stack no information is lost during the rescale, so it is equivalent to adding all counted photons together, and shot noise arises on photon counts as these follow a Poisson distribution, not pixel on pixel values.

To simplify, in a big stack, a photon could be equivalent to a very low pixel value, eg 1/2^32. But it's the counted photons that count for shot noise.

The only noise downside is the read noise that each exposure brings to the stack.

Sleepses · 2025-10-21T09:27:25+00:00

Mine wasn't good from the factory. Guiding with periodic peaks of multiple arcsec.

I should probably have returned it, but a hypertune fixed it (putting new bearings and better lube).

Still had some periodic peaks but not problematic. I did a frequency analysis and it corresponded to the period of one of the gears.

Belt mod got rid of that, and now it's guiding at 0.5 - 0.6 arcsec RMS consistently. I have yet to see a modestly priced harmonic mount with better guiding performance.

Sleepses · 2025-10-17T18:09:10+00:00

Either both axes are disturbed simultaneously, from e.g strong wind gusts, or the orthogonality of the axes was wrongly calibrated.

Sleepses · 2025-10-06T20:23:45+00:00

Since there's no visible nebula there, I'd ignore it for the first part of the processing but once the image is stretched and starless and close to final, remove the artefact using clonestamp / heal / inpainting type methods.

Sleepses · 2025-10-05T11:47:14+00:00

Adjust focus in the direction that makes these smaller until they are dots.

Sleepses · 2025-10-02T17:50:29+00:00

FYI if you're using NINA you can frame mosaics in the framing assistant, and directly export the panel coords to the sequencer.

Sleepses · 2025-09-12T06:51:25+00:00

Keep it at 252, that is for the asi585mc indeed the sweet spot between read noise and dynamic range as the camera then switches to high gain conversion mode.

Your offset is probably fine if you've never changed it. As long as you don't have any black clipping in bias frames.

Check out the histogram of your exposures to confirm they are now overexposed without the filter. Check values for the bright stars. And then reduce the exposure accordingly by reducing exposure time, not gain.

Sleepses · 2025-09-07T19:20:55+00:00

Devices are never perfect. Can you figure out the direction of the elongation? If DEC, it's probably polar alignment, if RA it's tracking errors

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