Thoughts on which imaging rigs to concentrate on

[Demonperformer]

I'm no expert, but it is all a balancing act between using a small aperture (big f number) and exposure length. So 60s at f2.8 is roughly equivalent to 120s at f4. I will often play around with single subs using a couple of apertures and a couple of sub lengths at the start and see which I think is going to give me the best results. I find that even the act of taking the subs can be an art rather than a science ... maybe this reflects differences in the way I set up as I do not have a permanent setup so have to do it every time. Unless the f4 subs look quite a bit better than the f2.8 subs, I will usually go with f2.8.

[alcol620]

Thanks Guys, up until today I had no idea what Stopping down the camera was, now I have done it! Wonderful the help you can get on here. Thanks again. Stopped down to 2.8 and see what I get from that, hopefully less awful stars. Need clear skies now

[happy-kat]

On really bright star targets you might want to stop down further to reduce chromatic aberration, try it and see if you get noticeable CA on a test shot.

[alcol620]

H-t and Dp as a non expert on camera technology, what is the effect of stopping down. Does the final image size stay the same?

[happy-kat]

Take your camera with lens on look down into the lens with f 1.8 now change it to f8 then look down lens a again and lastly repeat for f22.

The aperture blades cut light entering the sensor as the lens is stopped down.

[Demonperformer]

Stopping down will basically sharpen the image but it remains the same size & resolution.

[alcol620]

Hi everyone, have played around with different stops etc with the stock Canon 50 mm lens. Round stars to the center but anything but for the corners of the images.

Anyone like to say what lens they use, zoom or otherwise, that works well directly mounted on the ASI1600 camera/

thanks for feedback

[Gina]

WOW!  Been a while since I posted in this thread!.  I'm now looking at redesigning the 3D printed main frame and remote focussing system to achieve better results than the current arrangement and cater better for the new 8 hole ZWO EFW.  Currently the focus motor bracket is attached to the dovetail bar rather than the lens and when the camera is rotated the focus is lost.  I shall be designing a motor bracket that is fastened to the fixed part of the lens and will therefore rotate with it as the camera and EFW are rotated.  It would also be nice to arrange that the camera can be remotely rotated.

This is an earlier photo of the WF rig on the EQ8.

Edited December 4, 2019 by Gina

[Gina]

I'll bring the rig back indoors tomorrow and see what I want to do and decide if it would be worth arranging remote camera rotation.

[Gina]

3D printed a new set of focus gears and focus motor bracket that attached to the lens.  The camera can be rotated 90 degrees without affecting focus.  I got the opportunity to test this out last night and the focus is greatly improved - more so than I expected.

[Gina]

The success of last night's tests (in spite of a nearly full moon) has boosted my enthusiasm for astro imaging and led me on to further ideas.

With the vagaries of the weather here I feel I need to get the most out of any hours of clear night sky and also the most out of what equipment I have.  For instance I have two ASI1600MM-Cool cameras so a dual imaging rig seems something to go for.  I also have two filter wheels ZWO EFW and EFW Mini.  What I don't have is two sets of Astrodon 3nm filters but I can still split them between two imaging rigs.   Several of the vintage SLR lenses I have are in pairs of the same focal length.  My best telescopes are singles but I do have a pair of ST80s which are fine for NB.  APOs are only really needed for wideband imaging, mainly galaxies.  I may get on to planetary imaging later

I also have a pair of Evostar 80ED Pro scopes that were superseded years ago but could still prove useful.  I've been planning to sell them but scopes are awkward to transport and they aren't worth that much.  Having an EQ8 mount I have no problem with payload - I had 3 scopes on it at one stage some years ago but found getting all 3 aligned accurately was a problem.

I've thought out how I can run two virtually identical ZWO cameras on one setup.  I would use a separate RPi running INDIserver and drivers for each camera and 2 instances of KStars/Ekos on my indoor desktop.  One RPi would control the mount.  Two ZWO cameras of the same type can't run off one RPi as INDI is unable to distinguish between the two.

Edited December 10, 2019 by Gina

[Gina]

Firstly, the widefield rig.  I currently have a single imaging rig with 8 position EFW.  For a dual imaging rig I could add another camera and lens together with the ZWO EFW Mini 5 position.  For use on the EQ8 the two separate imaging rigs can be mounted on an aluminium plate, side by side, with the plate mounted on the dovetail. 

However, when I have the second pier and miniature observatory done, I shall want something smaller and lighter to use with my DIY mount.  For this I could perhaps have a fixed filter for one camera and the EFW Mini for the other.  This is shown in my Blog - Widefield Narrowband Dual Imaging Rig.  This would cater for my longest focal length pair of lenses of 200mm f4. 

The advantage of having the second pier etc. is that the EQ8 can be kept for telescopes and save humping heavy scopes or dual scope rigs on and off the EQ8.  Anyway, I have always liked the idea of building my own mount and the miniature observatory will make a great 3D printer project.

Edited December 12, 2019 by Gina

[Gina]

If my astro imaging enthusiasm is still intact in a year or two when I have the second pier/observatory up and running I might consider buying another cooled mono CMOS camera for use with smaller DSOs such as galaxies and MN190 scope but one with a smaller sensor and pixels such as the ASI 183MM-Cool.

[Gina]

Need dew heater om my 135mm f2.5 lens.  Thinking of about 2W and have 10Ω ¼W resistors. 

1. 13.8v supply. 
2. P=V²/R hence R=V²/P.
3. For P=2W, R = V²/2 = 13.8²/2 = 95Ω
4. Number of 10Ω resistors will be 10 near enough.

[wimvb]

That should do it. When I made one from resistors, I used higher value resistors in parallell. I found it mechanically more flexible. Resistors in series don't bend that well. The wire between the resistors can be multistrand to allow easier bending. If you have 1000 ohm, you can use 10 pcs also.

[Gina]

I have a 3D printed conical dew shield which fits on the lens and I drilled a series of little holes to take the resistor wires in a ring just in front of the lens.  The resisters were inside with the joins in the wires on the outside.  I covered the joints on the outside with hot melt glue.  Power to the dew heater is controlled from the RPi.

[wimvb]

My dew heater is just a resistor ladder with some 10 or so resistors in parallell. Soldered to two, stripped, multi strand copper wires and sandwiched between layers of duct tape. Short pieces of sticky velcro at each end to hold it in place. I've used this to warm a 135 mm lens and later around the stalk of the secondary of my 150pds. I have used it  with a pwm LED controller, but also on full whack with just a 12 V battery. "K-I-S-S" 

[Gina]

Sorting out back focus for the Esprit 80ED Pro field flattener and OAG.  Components are ASI 1600MM-Cool camera, ZWO EFW, 10mm extension ring, OAG, T2 to M43 adapter, Field Flattener, adapter, scope focuser.  This gives exactly correct back focus for the flattener.  Guide camera focus should also be about the same as the imaging camera.

Edited January 29, 2020 by Gina

[wimvb]

21 minutes ago, Gina said:

Sorting out back focus for the Esprit 80ED Pro field flattener and OAG.  Components are ASI 1600MM-Cool camera, ZWO EFW, 10mm extension ring, OAG, T2 to M43 adapter, Field Flattener, adapter, scope focuser.  This gives exactly correct back focus for the flattener.  Guide camera focus should also be about the same as the imaging camera.

The advantage of using zwo components all the way is that all spacers are included, either with the camera efw or oag. No need to buy extra. 

[Gina]

Yes indeed.

[Gina]

If I design and print a bracket for the focus motor that clamps onto the barrel of the focuser, I can have camera rotation by simply loosening the clamping ring that connects the focuser to the scope body.

[Gina]

Been going through my astro bits and pieces to see what I can do to collect more data and more difficult data.  Two main ideas - dual imaging rig and guiding.  I only have one 135mm f2.5 lens (which I'm using currently).  I also have just one 28mm lens.  OTOH I do have three 105mm f2.8 lenses and three 200mm f4.  Then it's a question of matching DSOs with appropriate lenses or telescopes (starting at 400mm f5).

The 105mm lenses give just under 30% more coverage in each direction than the 135mm.  This is a fairly small increase and I think would probably be alright for the DSOs I've been capturing with the 135mm lens.   I only have two ASI 1600MM-Cool cameras so I'm limited to a dual rig whereas a triple rig would be ideal, with Ha, OIII and SII NB filters.  In fact the 1600s are the only cooled cameras I have.  NO!!  I can't afford another!!

One DSO which is just too big for the 135mm lens but fits in the FoV of the 105mm is the AngelFish in Orion.

[Gina]

Now to look at the DSOs I've been imaging recently.

Flaming Star and Tadpoles.

Simeis 147 - Spaghetti Nebula.

 

[Gina]

Heart and Soul.  These don't fare so well - rather small for the 105mm lens but the 200mm looses some of the surrounding nebulosity.

Edited January 31, 2020 by Gina

[Gina]

NGC 7822 is one nebula that will fit nicely in the 200mm lens field.

As does IC 1396.