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@Anthony1979 If this helps then fine:

I shot the comet last night with a 70 - 200 zoom at f3.5. I used 2 and 2.5 second exposures at 400 iso.

I had to tweak the exposure in processing so 3 seconds would have been a better choice.

So it depends on your lens aperture settings. Based on the above for every 'f-stop' slower (bigger number) than f3.5 you need to double the exposure length or double your iso settings i.e. 400 / 800/ 1600 / 3200...

Best thing is to bracket well each side and check the results on the view screen. Ideally increase the iso rather than lengthening the exposure if your on a static tripod to avoid subject motion.

Good luck

How about boob of the day / month?

I'll kick off with this one...

Forgot to rotate the camera!

Thanks Pete @Pete Presland - I've added another image which is a stack of 5 x 2.5 sec subs. Smoothes out the background and (poss) extends the tail...

Perhaps a good topic for an imaging challenge?

Must check camera rotation before pressing GO!!!

I started out trying to make a 3 panel mosaic of ngc 7000 and surrounding area. Set up the panels in SGP's frame and mosaic press go and...

I looked at density /exposure on screen but didn't take enough notice of the image angle 🤬  Found out this morning when I transferred images from the laptop to main PC for processing.

Must try harder.

12-07-2020.  circa 00:15 - 00:30 ish.

70 - 200 mm lens on Nikon 800E 400 iso, 2.0 - 2.5 sec exposures focal lengths vary.

Hope you like.

I've used the SA with a WO ZS73 and finder guider attached. Like @symmetal says PA is all important with the SA. I've managed 5 min subs with this combo.

If you're a planetary person then a good one of 10mm or less, if it's DSO's that float your boat then a good one 18mm or more. Wide apparent FoV's make quite a difference - try before you buy.

On 19/03/2020 at 16:50, lukebl said:

Can someone help me here?

Now, I know there are endless threads on the web about collimation, but I can't get my head around this problem. Please bear with me while I explain.

I am now the proud owner of a Howie Glatter collimator, complete with the Concentric Circle attachment. It's a gorgeous piece of equipment. Shiny, solid, heavy and beautiful. One of the best, I'm led to believe. I thought that it would be the solution to collimating my 200mm Ritchey-Chretian.

So, I have gone through the two main stages of collimating it:
1: Align the focuser with the secondary mirror, so that the red dot aligns with the little secondary centre circle
2: Adjust the secondary so that the circular pattern projects evenly over the primary mirror.

I've done these stages and it all looks good as shown below. Nice concentric circles on the primary and when projected onto the wall. So I shouldn't need to collimate the primary.

HOWEVER, when I set it up and aim on a star, it doesn't look right and the out of focus image looks like the view on the left in this image (this isn't my image, but it shows the general effect). It's not camera sag, as I've tried it in all positions.

So I then re-adjust the secondary collimation so that the out-of-focus star looks like the version on the right.

Although the focus and collimation look good by eye, when I re-insert the Howie Glatter I get the projection show below. Which suggest that the collimation is out, when my eye says that it's not.

So what is going on here? Is the Howie Glatter faulty? I thought they were the best. Or what else is going on?

You've missed a stage or two...

1 align the focuser to point directly at the secondary (use the pencil beam for this)

2 align the secondary so the pencil beam is reflected directly back at the focuser. (There will be a set of diffraction rings seen around the Howie which help with this alignment)

3 change the filter to the concentric ring pattern. It should produce a set of reflected rings on the primary mirror.

4 make sure your OTA is level and as orthogonal to a screen/wall as possible. You will see the ring pattern projected on the screen/wall

5 adjust the primary mirror so the shadow of the secondary housing is concentric with the innermost visible bright ring.

6 star test and tweak the primary only to produce a circular doughnut shape of a slightly defocused star (Polaris not the best as it's a double).

Once you've aligned the focuser and secondary to each other leave them alone.  All further adjustments are on the primary mirror only.

The Howie filters should be positioned approximately at the focal plane of scope when set to infinity for the exit ring pattern to be parallel.

Whilst the focuser/secondary separation isn't critical for their alignment (steps 1&2), their separation is critical for regarding the design focal length of the scope.

Like the righthand image as the nebulosity stands out more. But I think it could edge just a touch to the left without impacting on the nebulae...

11 minutes ago, Adam J said:

Is that filter rated to work at F2? Might explain the halos. 

Not quite they don't commit themselves to f2 but show examples at f2.8, at f2 the H-alpha end suffers a little to me but playing with the processing seems to revive it. I'm thoroughly enjoying this scope/filter combo.

On 03/06/2020 at 14:45, Northernlight said:

Francis - Are those Halo's around the bright starts internal reflections due to the filter ?

Yes they're caused by the filter but for a reason: the only way I could fit the filter at the time of shooting these images was with the wrong side to the sky. The spikes within the halos are from the cables to the camera crossing the light path.

Here's an image with the IDAS NB-1 round the right way, the spikes from the cables are still there but the halos have gone:

Initial thoughts on a filter draw. Filters would need to be removed from screw mounts to allow a thin enough tray/holder to be used but definitely looks promising.

Side view attached showing front end of the Horizon II (drg from Atik website). Black rectangle shows the CMOS chip, red rectangle - a filter. Grey areas show the approximate cross section of the adapter. The adapter would be in two halves to allow machining of the filter tray registration slot... TBC.

12 hours ago, knobby said:

Possibly a dumb observation but surely you can't just put the 1600 in place of the 294, you'll need a filter holder of some sort or are you just going sole mono ?

I have a Baader filter draw enabling me to manually change 2" filters. That wouldn't be an option with the Horizon. But I'm not giving up on the Atik yet. I'm trying to see if I can make the short extension tube for the Atik able to take filters but it's going to be really tight.

2 hours ago, david_taurus83 said:

Which features are you talking about?

Originally I wanted the Atik mainly because of the UK customer service and the reputation they have for quality but I was swayed by the cheaper ZWO which comes with all the adapters you need. Rarely hear about issues with the ASI1600 anyway. I assume your aware of the microlensing issue of this sensor which will affect both Atik and ZWO versions.

The comparison: http://www.astrosurf.com/buil/atik_vs_zwo/

As for the ASI1600MM Pro coming with all the adapters I need - they are all surplus, I can't use any of them because the back focus on the RASA 8 at 25mm wont allow it. I like the 1600 because it has the same 6.5mm BFD as my 294MC so I can make a simple change over of the cameras. However it would be quite a simple task to turn up a short custom spacer to match the Horizons 13mm BFD with 42 x 0.75mm opposing threads.

I use an ASI294MC Pro and an IDAS NB-1 filter quite often

Couple of my images:

2 hours ago, andrew s said:

If you Google "Christian Buil spectroscopy" he does a comparison which should help you even though it's the older Atik Horizon.

Regards Andrew 

Thanks @andrew s for that prompt to Christian Buil's site. Cameras are almost identical, just little things ZWO and Atik have tailored to their markets. One thing I hadn't realised is that the Atik Horizon has to be powered to be used unlike the ASI1600MM Pro which (like the ASI294MC Pro) can be used via USB cable only although there's no cooler operation. I've certainly used that feature with the 294. Some features of the 1600MM Pro can't be accessed via Ascom whereas the Horizon can. All a bit swings-n-roundabouts...

I have a RASA 8 inch and use an ASI 294 MC Pro OSC cooled camera on it. I'm thinking about a mono camera of similar 4/3rds format. The ASI1600MM has the same back focus as the 294MCP simplifying a camera change over. The Atik has a 13mm back focus requiring a shorter extension tube to meet the back focus requirements of the RASA 8 (25mm BF) so not a real problem as the camera + it's short extension can be swapped together.

My real dilemma is not knowing either the 1600MM or the Horizon II. I really like my ASI-294MCP, but I've owned an Atik 383L mono and really liked that so both manufacturers have my confidence.

I image DSO's almost exclusively, never tried EAA and not particularly interested in planetary, solar or lunar imaging.

If anyone has experience of these (one or both) I'd like your thoughts/comments please.

Keep Safe

Superb Carole - fun indeed👌

I think it's Arcturus. I've overlain a CdC screen shot and matched the star patterns and your bright do lines up with Arcturus almost exactly.

Hi @JeffM , Although the extra weight took the SA to it's limits it also smoothed things down and with a careful PA I've found I can get 3 min subs quite easily. I've now sold the SA and moved to a CEM25P with the WO 73.

The SA and ZS 73 (+flat73A) are a great little combo not just for grab and go stuff.

8 hours ago, AndyThilo said:

I want the original screws though, I have Bobs Knobs, I want rid of them 😊

Sorry not what I meant. They sell Bob's knobs so they will know the thread size and form. Probably a UNC 3/16"

Try FLO they sell Bob's knobs - great bunch sure they'll help you out

After the trials of earlier this week I started by tweaking the PA with a drift alignment, running PHD's guide assistant and checking with 15 x 180s subs on M51. New set of flats too.

Result.

Processed in PI and touched up in PS.

I've used UPS and DPD to send musical instruments overseas and across the UK. Bit like glass most won't insure musical instruments. Something to think about is insuring the object(s) via a temp upgrade to your other (house) insurer. 

Here's my attempt. Mainly working with Curves transform, Saturation, Histogram transform, SCNR, with and without a luminance mask...