Stub Mandrel

2 hours ago, Fitzroy Clarke said:

I am a member a couple hours  and I am indeed very impressed 

I have one request info on which of these two Cameras will be better to own, 
ASI 183MC  Pro or  ASI178MC

Many thanks

Agreed, start a new thread in the camera forum.

This is a question I wrestled with, it depends on what scope you have to some extent.

2 hours ago, g-rex said:

Some amazing images. It certainly won't be the telescope that'll be the limiting factor!

Stub Mandrel, do you polar align using the polar scope or some other message?

For all those I used a polarscope with the new-style reticle.

So polar alignment is now an international competition? I see you can even share your PA on social media...

"Global ranking 414 Defeated 38.8% ASIAIR Users"

I woudl be interested except it still doesn't work with ASI120MM/MC 😕

1 hour ago, Alien 13 said:

The Pluto trigger is basically a smart wireless DSLR shutter remote control that is operated via a phone app, the unit has built in sensors for sound and light triggers so can detect lightening strikes for example during the day as well as doing HDR or just used as a intervalometer. The app is very powerful and allows for lots of differing configurations.

Alan

Made me go a-googling Alan:

https://plutotrigger.com/products/pluto-trigger?variant=26846149383

It's very impressive, there's no individual function that's particularly innovative - except they've packed EVERYTHING you might want for automated photography into small box at a reasonable price.

good to revive this thread a s more people should be aware of this option!

Another amazing display of France's capacity to place vegetables in orbit...

Just missed it, but worth watching again for the auto translate...

Pleased with this, I think I'm getting the hang, although with only 12 5-minute frames I would like to get 2 or 3 times the data to control the noise.

First though, I'm going to cut some teeth on OIII and SII.

Combined with some RGB for a few years back as L.

I think I found the problem.

Looks like I had dark subtraction on in Sharpcap when I took the lights, but not the flats (or the flats had additional subtraction of the wrong dark).

Last night I took my lights with dark subtraction, then took flats with correctly timed darks subtracted and stacked without darks or bias and it worked fine 🙂

On 04/01/2020 at 14:11, g-rex said:

Could you advise me on roughly how long an exposure I could get unguided?

60 seconds to two minutes if you don't pixel peep and you have it set up nicely.

Al;l my images on this thread up to June 2017 are unguided, some of them use 120s exposures. These are both 130P-DS, unguided on an EQ3-2, 120s exposures:

On 22/12/2019 at 17:14, Nakedgun said:

Here is the oldest scope I own, made perhaps during the 60s.

I got one of these, gives really nice views of the moon and yes you CAN SEE SATURN'S RINGS!

I almost forgot to process these, about 55% of  70-odd jpegs taken with my bridge camera. Filling in the gaps in my moon collection, I have very few from the last quarter.

The sky still had colour to it, so I didn't convert to mono. Nothing to write home about, but a pleasant image with minimal processing after stacking, just light deconvolution and gentle curves.

Nadolig Llawen - a Merry Christmas to one and all 🙂

What @Stu says... I've really gained loads form joining our club, it's a big, active one and we are soon to commission our observatory, we have courses, talks and informal events. It was a clear night last time we had our 'informal' meeting and there were 20-25 of us imaging and observing at about -2, some of us until well after midnight.

But the best thing about it is regularly meeting up with a great bunch of people who enjoy discussing our very peculiar hobby! It's very friendly (it's not cliquey) and new (and longstanding) people get help and encouragement , lost of us put in time as volunteers etc.

We meet up to go to shows, observing/imaging etc. its not just club meetings.

Many of us have even been sharing photos of Christmas presents etc. today.

The Ikea box came, and it's a perfect fit for the 15" screen laptop.

I need to add some sort of front cover, probably just a piece of fabric. Hopefully the heat from the computer will create a slightly warmer micro-climate inside.

On 21/12/2019 at 10:51, alexbb said:

That happened to me too some time ago. There might have been multiple reasons for this, but I tried to do everything right. Same temperature for lights and dark, same temperature for flats and dark flats. I also see that you're using a newtonian so make sure you don't have any light leaks. I cover the end of my newtonians always (lights, calibration) and try preventing light leak through/around the focuser too.

I suspect you might have some light leaking into the OTA.

Could be, but I've been using this setup for three years with a DSLR and haven't had the same issue (I have had nights when the subs have been too poor to get anything though).

Here we go, comparison of flats from 9th and 17th of December  - you can see I got rid of the dust bunnies for the second run... both auto stretched.

The one on the left was used for the heart nebula image above. This makes me pretty confident it is something about my subs, rather than a problem with the flats.

5 hours ago, david_taurus83 said:

I still think those flats arent right Neil. See below a sample of mine. First 2 are a single flat unstretched and stretched. Second 2 are master flat unstretched and stretched. Also note how narrow the foot of my histogram is compared to yours, so theres a large deviation of pixel values in your flats. In both my examples, my 4 corners measure circa just under 21000 ADU and the centre is just over 22000 ADU. I suspect that your example will have a much bigger difference between corners and brightest part in the centre. Its the same camera but the difference is I used a refractor. FWIW I always struggled to take propoer flats on my old 200P.

I think its a bit misleading to use the histogram from DSS, it looks skinnier in other programmes.

I suspect it's either something to do with SharpCap settings OR an issue with my subs. I lean towards the second as I didn't have this issue the first time I use the ASI1600.

The big difference is thAt this is narrowband, the images with the dark spot are with an L filter. Ironically the flats for both sessions were taken with the L filter, so the problem session should be better matched!

See - no problem I can see here (aside from framing and slightly soft focus):

On 19/12/2019 at 23:11, wimvb said:

Next you could check your dark master, but this is also a likely candidate:

If the problem persists, it's vey likely something in the calibration process, but otherwise atmospheric conditions could be to blame. Are all subs affected equally, or are some subs worse than others?

It seems all subs are affected equally.

All I can conclude is that, for some reason, the flats just aren't matching the subs.

Bought a new W10 laptop with an SSD in it... boots so fast it even impressed my daughter who has a Macbook 🙂

3 hours ago, wimvb said:

If you suspect the calibration process of the master flat, try calibrating one flat frame with the master flat, and the master flat dark. This should give a completely flat flat.

Looks like the process is OK, allowing for the fact my LED flat screen probably has a gradient (I rotate it to eliminate this) the result is pretty even, certainly no big dark (or light) spot in the upper middle:

Linearly stretched to show the very smooth residual gradient, this is just because the LED panel is brighter on one side - bear in mind that it's always worked fine for my other camera (and last week with this one!)

2 hours ago, wimvb said:

If you suspect the calibration process of the master flat, try calibrating one flat frame with the master flat, and the master flat dark. This should give a completely flat flat.

I guess that this means that the originals are NOT 8 bit, and that lights and calibration frames are all the same bit depth.

Yep, everything is 16 bit. (12 bit really).

I'm not 100% sure, but I suspect the problem is that my image has virtually no detail (conditions were far from good) and that I'm just stretching it far beyond what the data will allow.

3 hours ago, david_taurus83 said:

Hi Neil. The stretched master flat looks too bright in the middle. Try taking them again and output everything in FITS. I have made the mistake in Sharpcap before. Spent a whole day doing a dark library to find out after the output files were png or something daft.

Hi David, still set up. I've taken another set as FITS. Also, I've done them without the dewshield - previously I've always done them without it. Fingers crossed.

I'm having trouble with flats over correcting in DSS. This hasn't been a problem for me with DSLR images unless I made silly mistakes.

I'm using an ASI1600MM, all frames (lights, darks, flast, dark flats taken at -20C), flats are taken using a flat panel with an extra layer of diffuser, rotated between frames (24 of them). I've greatly reduced the sample images in size and these are 8 bit too.

Here's the unstretched master flat, clearly not over or under exposed (I checked the histogram):

Here's a stretched master flat which looks sensible enough:

Here's the result of a stack, with a quick stretch in DSS, note the over darkened centre:

I can't help noticing that the dark area looks suspiciously 'square'...

For completeness, stack without flats:

I've tried stacking with and without darks and with and without dark flats, and with and without checking 'set the black point to zero'.

The only things I can think of are that:

1 - I used TIFF this time for Lights, Flats and Bias, I didn't have this issue when I used FITS (sharpcap generates a master dark that's a FITS).

2 - Dark subtraction may have been switched on when taking the lights.. but if this was the problem not using a dark should surely have solved the issue?

Has anyone got any suggestions?