First Attempt @ AP

[DaveHKent]

On 23/10/2019 at 16:29, cjdawson said:

Funny you should say that,  I just purchased a setup that I think is capable of getting the whole thing in one go!

Camera: Canon 70D (though my ZWO ASI1600MM-PRO would also work here)

Telescope: William Optics SpaceCat 51

Mount: Sky-Watcher Star Adventurer Pro pack

Tripod: Sky-Watcher Stainless steel 3/8"

Guide Scope: ZWO Mini guide scope

Guide Camera: ZWO ASI290MM (Had this looking for a good use)

Guide computer: Raspberry PI 4, running PHD2.   (ASIAir looks very interesting for this application as well)

 

The key think here is that the SpaceCat is only a 250mm Focal length, which is what gives the wide field of view.   This is much much wider than I could get with my LX-90 and all the most powerful focal reducer that I could get my hands on.

 

I got a SA earlier in the year and I'm just getting to grips with it? Does the auto guide just correct for slight imperfections in polar alignment?

I've got a Canon 700D, a ZWO ASI1200MC and a number of raspberry pi sitting about. With the scope from my Celestron NexStar 90SLT (90mm ap, 1250 focal length) being able to screw straight onto the Star Adventurer, I was hoping that just the purchase of a guide scope would give some very good images for not much extra cost.

[wimvb]

5 minutes ago, DaveHKent said:

I got a SA earlier in the year and I'm just getting to grips with it? Does the auto guide just correct for slight imperfections in polar alignment?

As far as I know, the SA only has one motor: RA. It can't correct for any drift in DEC, which you will get if polar alignment is off. It will correct RA drift, and fluctuations in RA tracking.

[Davey-T]

57 minutes ago, DaveHKent said:

With the scope from my Celestron NexStar 90SLT (90mm ap, 1250 focal length) being able to screw straight onto the Star Adventurer,

I have one of those scopes that I tried on the Star Adventurer but it didn't work very well, I think it was just a bit too long.

Do you have any camera lenses as they work very well.

Dave

Edited December 8, 2019 by Davey-T

[wimvb]

3 hours ago, Benjam said:

Here's the file https://www.dropbox.com/s/dpua2fvrfk8jw5e/Autosave001.tif?dl=0 

@wimvb @alacant

Kind Regards

Ben

Downloaded. Some first remarks

1. the target is a bit off center, but it fits the fov very well

2. you need to take flats. There is strong vignetting, which combined with large offsets between subs, creates a gradient that even DBE in PixInsight struggles with. I had to apply two passes of DBE to get a reasonably flat background. There is also a dust bunny in the image that can't be removed.

[wimvb]

Here's my attempt in PixInsight

• Crop
• DBE x2
• Background neutrlisation
• Photometric Colour Calibration
• Split Luminance

RGB:

• Star repair script
• Masked stretch
• Further star repair

Luminance:

• Histogram transformation
• Curves Transformation
• HDR transformation
• Curves Transformation
• LRGB combination

LRGB:

• LRGB combination
• Star reduction
• 50 % resampled

[Benjam]

1 hour ago, wimvb said:

Here's my attempt in PixInsight

• Crop
• DBE x2
• Background neutrlisation
• Photometric Colour Calibration
• Split Luminance

RGB:

• Star repair script
• Masked stretch
• Further star repair

Luminance:

• Histogram transformation
• Curves Transformation
• HDR transformation
• Curves Transformation
• LRGB combination

LRGB:

• LRGB combination
• Star reduction
• 50 % resampled

Wow, looks better then I had imagined. Thank you Wim. 

Yes I do need to work on centring the object and flats next time, something I haven’t done as yet. 

Two questions.

1) What dose DBE stand for? 

2) What’s a dust bunny and could you highlight it please.

Thank you once again 

Ben 

 

[wimvb]

12 minutes ago, Benjam said:

What dose DBE stand for?

Dynamic Background Equalisation: a tool in Pixinsight to remove gradients in the image.

13 minutes ago, Benjam said:

What’s a dust bunny

The shadow of dust near the camera sensor. This will cause a dark area in the image. Only flats will help even these out. 

16 minutes ago, Benjam said:

could you highlight it please.

"no can do". I toned it down as much as possible. It's just below the bright stars above the galaxy. I can post an image where it's still visible. 

[wimvb]

Here's the image with only a crop and a basic stretch applied. The vignetting and dust bunny are obvious. DBE removes the vignetting, which makes the dust bunny even more obvious, as it becomes the darkest area in the image.

and as received (stretched):

 

Edited December 8, 2019 by wimvb

[Benjam]

Thank you  @wimvb  for processing my data. It’s given me hope and encouragement to improve next time around. For the flat frames, I’m going to buy a light frame from Amazon. 

The data I collected was 102 lights but because of drift I think DSS only stacked 80 x 90 sec @ 200mm. I could try for 200 lights next time and maybe increase the focal to 250mm. Also adding flats, bias and darks frames. 

I honestly can’t wait to try again!!! 

Ben 

 

Edited December 8, 2019 by Benjam

[carastro]

I had a go.  Just for the future, try to learn to do flats as the dust bunny by the interesting star pattern above shows up.  I managed to deal with the Vignetting using gradient exterminator, but again flats would deal with this and it's not always possible to use GE to sort out the vignetting.

I also did a crop for a close up. 

Carole 

[DaveHKent]

3 hours ago, Davey-T said:

I have one of those scopes that I tried on the Star Adventurer but it didn't work very well, I think it was just a bit too long.

Do you have any camera lenses as they work very well.

Dave

Cheers, I'll give it a go anyway. I do have a 75-300mm lens.

What is the longest focal length you think the SA can cope with?

[Davey-T]

15 minutes ago, DaveHKent said:

Cheers, I'll give it a go anyway. I do have a 75-300mm lens.

What is the longest focal length you think the SA can cope with?

Up to 300mm works well, mine can do a couple of minutes using one.

Dave

[cjdawson]

6 hours ago, DaveHKent said:

 

I got a SA earlier in the year and I'm just getting to grips with it? Does the auto guide just correct for slight imperfections in polar alignment?

I've got a Canon 700D, a ZWO ASI1200MC and a number of raspberry pi sitting about. With the scope from my Celestron NexStar 90SLT (90mm ap, 1250 focal length) being able to screw straight onto the Star Adventurer, I was hoping that just the purchase of a guide scope would give some very good images for not much extra cost.

I'm not sure how heavy the NexStar 90SLT is, I'm wondering if it's a little on the heavy side.   If you have it already, try it out can't hurt if it's costing nothing for the attempt.     MY SpaceCat51 is all aluminium case so it's quite heavy, especially when I have the 70D and battery grip installed.   The way that I use my camera's with my scope gives me a double hit that makes for better results.    Firstly, using the guider to do the polar alignment, means that the error is normally less than 2 seconds of arc!    Then over the session, the autoguiding keeps the image steady.  (more on this below)

6 hours ago, wimvb said:

As far as I know, the SA only has one motor: RA. It can't correct for any drift in DEC, which you will get if polar alignment is off. It will correct RA drift, and fluctuations in RA tracking.

Yes.  The Star Adventurer only has an RA motor, which means that the mount will only allow auto guiding in RA.  Any DEC error will cause drift over the imaging session.   My setup was to use a wide field scope.   i.e. the SpaceCat 51 which has a 250mm focal length.  So when you pair that with an APS-C DSLR (Canon 70D in my case) or a ZWO ASI1600MM-Pro (and EFW) you end up with "under sampling" which means that the camera is capable of taking more detail than the lens can provide.  This has the benefit of loosing some of the guide errors in the fact that the pixels are covering a larger area of sky due to the short focal length.     The other side effect of this is that you can take longer exposures before you need to guide.    For the length of exposures that I've been taking, the stars are round and stay that way for the whole session.     In the worst session that I've done with this setup so far, over 4 hours, the image did drift quite a way, it's noticeable after stacking, but each sub frame doesn't look too bad.  As I was guiding on RA, the only shift was in DEC which also meant things were not as bad either.  I'd still have pefered to have had the DEC closer.

1 hour ago, Davey-T said:

Up to 300mm works well, mine can do a couple of minutes using one.

Dave

I agree with this.  After getting the PA done, without guiding a couple of minute exposures should be possible.  And with the ISO turned up, you shouldn't need exposures that long either.

 

To give some idea, here's an LRGB image that I made last week of M45.     I did have a problem with it.   I think I have sorted out the problem of the diffraction spikes (it only happened on the L Channel)

 

This was my first attempt at taking the horsehead and flame. I'd also not completed a full LRGB image before.  I've left it uncropped, so that you can see the amount of DEC guiding error that I had over the 2 hours

 

This image of M32 is a colour image taken with my Canon 70D from Kielder forest... on a misty night!  The transparency was rubbish, but the atmosphere was stable because of all the water vapour.  Lots of people had given up trying to do anything, but my plucky little Star Adventurer had a go anyway.  This was the result.   This is a set of 120 * 1 min subs at IIRC iso 6400.  Next time, I think I should turn the ISO down a little.

 

I think my experience so far with the Star Adventurer boils down to this....

1. make sure that you have a good tripod.  I use a steel one from Sky Watcher.

2. make sure that you don't overload the mount.  My SpaceCat, GuideScope, RedDot finder combo is the heaviest setup that I plan on putting on it.

3. Take you time setting up, That polar alignment is all important.   Get that right and the rest becomes a pleasure.

[Benjam]

Hi everyone, will this work for taking flats? I’ve checked the dimensions and the light box linked below will be plenty big enough to fit over a 8” SCT. https://www.amazon.co.uk/dp/B01HEQAFQQ/ref=cm_sw_r_cp_tai_D4o8DbQ7GEVZS

I also practiced centring my target last night and ended up taking 50 subs.

[wimvb]

25 minutes ago, Benjam said:

Hi everyone, will this work for taking flats? I’ve checked the dimensions and the light box linked below will be plenty big enough to fit over a 8” SCT. https://www.amazon.co.uk/dp/B01HEQAFQQ/ref=cm_sw_r_cp_tai_D4o8DbQ7GEVZS

It depends. There is a thread in the imaging section about these. The consensus seems to be that if the leds are situated at only one side, illumination will be uneven, and it won't work. But if illumination is even across the surface, it will work if you cover the panel with white paper. Have a look here 

 

Edited December 11, 2019 by wimvb

[wimvb]

Here's how I take flats. 

https://www.astrobin.com/326547/?nc=user

IKEA Floalt + embroidery hoop with 4 layers of white cotton. The Floalt has intensity and light temperature control. Together with the automatic exposure control in Ekos/Kstars, it produces good flats. 

[don4l]

1 hour ago, Benjam said:

Hi everyone, will this work for taking flats? I’ve checked the dimensions and the light box linked below will be plenty big enough to fit over a 8” SCT. https://www.amazon.co.uk/dp/B01HEQAFQQ/ref=cm_sw_r_cp_tai_D4o8DbQ7GEVZS

I also practiced centring my target last night and ended up taking 50 subs.

That looks like it should be fine.

I recently bought this one :- https://www.amazon.co.uk/gp/product/B00OJ9PQWU/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[edit]  I've just seen Wim's post, and I am fairly sure that mine produces an even illumination.  It may be too bright even on the dimmest setting - I'll find out when I test it.  There is a photo of mine illuminated in the "what the Postman..." thread :-

=====

Posted November 6

A new A3 Light box which should make a cost effective flat field source.  Having tested it,  I'm also thinking that it would make a decent light for an observatory or shed.

 

I haven't used it as a light box yet, but it looks fine.  It arrived promptly, was well packed and has it's own power cube.

Edited December 11, 2019 by don4l

[Benjam]

I've created another stacked image using DSS if anyone would like to be kind enough to pull any detail out. Also I've just signed up to the Pixinsight 45 day free trial.

https://www.dropbox.com/s/kvmyfkhlr9rh6v2/M42.tif?dl=0

M42 

50 lights

25 darks

25 bias

Still no flats, though I'm currently working on this... 

Kind Regards 

Ben

 

[wimvb]

1 hour ago, Benjam said:

I've created another stacked image using DSS if anyone would like to be kind enough to pull any detail out. Also I've just signed up to the Pixinsight 45 day free trial.

https://www.dropbox.com/s/kvmyfkhlr9rh6v2/M42.tif?dl=0

M42 

50 lights

25 darks

25 bias

Still no flats, though I'm currently working on this... 

Kind Regards 

Ben

 

First impression: Great image. Unfortunately it still suffers from the dust bunny in the top half

Simple stretch and some HDR compression in PixInsight

[Benjam]

OMG, wow, I can’t believe this is the same picture. Thank you Wim! 

Hopefully the light box @don4l mentions will help me with flats. 

Ben 

 

 

[wimvb]

10 minutes ago, Benjam said:

Hopefully the light box @don4l mentions will help me with flats. 

Ben 

 

 

I had a look at it myself, but unfortunately none of the vendors ship to Sweden. Over here, these usually are a lot more expensive.

Btw, I can only recommend PixInsight, it has a different philosophy than other apps, but it has everything included. No need to get plugins or addons. It's well worth the money.

[Benjam]

38 minutes ago, wimvb said:

I had a look at it myself, but unfortunately none of the vendors ship to Sweden. Over here, these usually are a lot more expensive.

Btw, I can only recommend PixInsight, it has a different philosophy than other apps, but it has everything included. No need to get plugins or addons. It's well worth the money.

I was watching this earlier on YouTube, the video was made by another SGL member. 

PixInsight Auto Script - Auto processing. I like the idea of this, especially for a beginner like me. 

Ben 

 

 

[wimvb]

Put a little more work into it.  Noise reduction, colour contrast and repaired the stars.

[wimvb]

46 minutes ago, Benjam said:

I was watching this earlier on YouTube, the video was made by another SGL member. 

PixInsight Auto Script - Auto processing. I like the idea of this, especially for a beginner like me. 

Ben 

Where's the fun in that? For me processing raw data is where the challenge is in AP. Data capture is very much a mechanical activity, while processing is the artistic part of our hobby.

The problem with this set of scripts is that you hand over control allmost completely. One of the advantages of Pixinsight is that it lets you take control of all the details in post processing. Daunting at first, but powerful once you understand. Besides, every image has its own challenges, which I don't think you can solve by applying a single script. Some of the shortcomings of the scripts shown in the video were the cropping of all four edges equally (that would have clipped your M42), leaving a stacking artefact on the right hand side in the image, the green cast that could have been removed much more efficiently without creating a purple/magenta background, etc.

For a beginner I can recommend the videos by Richard Bloch (just Google Richard Bloch PixInsigt), and Kayron Mercieca (lightvortexastronomy.com), as well as our in house guru Harry Page.

[Benjam]

@wimvb I’m truly blown away by the image you’ve produced, Thank you. That was just 50 subs @ 20 seconds. 

What confuses me is the amount of red colour. I presumed because I’m using a non modded camera then I wouldn’t be able to capture any redness in the nebula.

I don't think I’m a arty kinda person but I’m willing and keen to learn new skills. I will watch the videos you’ve recommended. 

 I think I may have another attempt at M42, though this time piggybacking the camera and capturing the whole nebula. 

Ben