alan4908

A reprocessed attempt to improve the nebula contrast and stars of this LRGB image of the Christmas Tree cluster.  It also has an Ha blend into the Red and Lum channels. The original can be found in my album under Deep Sky III.  

Alan

9 hours ago, Datalord said:

The questions are: should I use non-perfect subs while stacking or will it only do harm? Can the stacking algorithms figure out to cancel out the non-focused bits when applying weights? Will I get the reduced noise I think I will by adding them?

Personally, I think it depends on what you aiming for in the final image.

If you use subs which have trails then if you include them and you use a sigma clipping algorithm then you will find that your final signal to noise will be higher that if you had excluded them but this approach will effectively introduce a slight blur into the final image.  The more you include the more blur and the more chance that you will end up with non round stars.  However, this may not be noticeable, particular if you are considering an LRGB approach and the non perfect subs are in the RGB data.  

If you have lots of subs (> 15) of a particular channel then I would suggest you use the Pixinsight stacking option of Winsorized signal clipping - provided that the number of non-perfect subs is relatively small in relation to the total number, then I would suggest including the trailed subs, obtain the result and then compare it to the result when you only include perfect subs.  

If you have the data, then I would encourage you to experiment. 

Alan

Hi Brian

On the subject of fiddling with sliders to get pleasing images from a Hubble mapping, I suggest you take a look at this tutorial: http://bf-astro.com/hubbleP.htm

Alan 

I decided to try out some star manipulation techniques with the objective of making the Cocoon stand out a little more from the star field.  For those who may be interested I used:

1. A PI circular Kernal erosion filter on the bright stars.

2.  A PI star de-emphasis technique on the lower/medium bright stars. 

3. A PS radial blur on any wonky stars.  

Alan

15 hours ago, PhotoGav said:

Thank you Alan. I have Aladin and have tried to use it in the past, but found it very confusing and gave up embarrassingly quickly! I will give it another go. There must be a decent tutorial for it somewhere...

I don't know about a tutorial but you may want to check that you have a the latest version since it changed recently making it more easy to use.  When you have it.... just enter the search item (M63) wait for it to show a picture of M63, then click on the SIMBAD layer - this will overlay the image with anything interesting via square boxes. One of the boxes will relate the galaxy, hover the mouse over this box and click - this will bring up the details of the galaxy. 

Alan

Nice processing Gav !

On the faint galaxy front, the lower one of these appears to known as 2MFGC 10580. I cannot see any info about the other one. 

I suggest you download the (free) program Aladin, which acts as a graphical interface into the NED and SIMBAD etc databases - it will allow you to do a comprehensive search.  

Alan 

4 hours ago, Rodd said:

I think you can back off the stretch a bit--image is very bright and stars look like they are a bit bloated.  I think if you dim the histogram a bit the details will pop even more.  Nice close up

Rodd

Thanks for the comment Rodd. 

Yes, I agree the image is bright but I quite like this level which is primarily to highlight the gaseous white parts of the nebula. If you hover around the image you will find that parts of it are actually very dark. 

I agree that some of the stars are large but since they are are bright and the image is cropped, I personally think that is OK - but again thanks very much for your comment  

2 hours ago, carastro said:

I like it,

I think this target looks good both as a close and as a wider field which shows the dark Nebula but then you lose the detail in the cocoon.

I found when I cropped my image I got large stars too.

Carole 

Thanks Carole - I think I am coming the conclusion that I am more of a details man. 

Alan

12 hours ago, Dark Horizon said:

Nice image. However i much prefer this with a lot more space around it, there's so much more to this target. Great pic all the same

Thanks for the comment.

Yes, I agree that there's quite a bit going on around this nebula, here, I was interested in gathering details - if you want to see a more wide-field shot have a look in my album Deep Space Sky II which contains images from my SW ED80.  Maybe I should try to combine the two images with Registar 

Alan

The Cocoon Nebula (IC5146) is located in Cygnus and is both a reflection and emission nebula.  It's about 4000 light years away and spans 15 light years. The emission nebula, consisting of glowing hydrogen gas appears red whilst the reflection nebula appears blue.  It also contains an open cluster of young stars which includes the bright star seen at the centre of the nebula, below. 

This LRGB image image has an Ha blend into the red channel and was taken with my Esprit 150. It represents an integration time of about 27 hours.

I hope you like it !

Alan 

LIGHTS:  L:13, R:13, G:12,B:9, x 600s Ha: 39 x 1800s. DARKS: 30, FLATS:40, BIAS:100 all at -20C.

On 18/06/2019 at 16:40, Chris M48 said:

I can’t seems to get good focus with my SW ED100 Refractor.

Below is an example of a typical image taken with my T3 (1100D).

It’s an APO doublet so I’m very wary about disassembly.

Any suggestions please?

Hi Chris

I suggest you download a free trial of CCDInspector (https://www.ccdware.com/products/ccdinspector/) which will enable you to quantitatively evaluate your focus, camera tilt and curvature.  In order to do this accurately you need to put it in averaging mode (say 5 images) and feed it calibrated but unstacked subs. Whilst you can use it on processed images, it can give very misleading results.  Having said all that...... if I put your image through CCDInspector it does indicate that you have quite a bit of camera tilt (12%) and your star aspect ratio is 20 which isn't great.  If you put the image through PI's aberration inspector you can clearly see the effect on the stars at different points of the image see below (top left/bottom left/center/top right/top left).

Poor aspect star ratios can be created by poor guiding and camera tilt can be caused by focuser droop. So, to reduce any errors created by your mount and reduce focuser droop, I'd suggest pointing your scope vertically and taking 5 very short exposures (eg 10s) and then feeding these individual subs through CCDInspector  and examining the result. By using this methodology you should be able to decouple focusing issues from other effects. 

Alan

45 minutes ago, alan potts said:

what is a good figure to aim for?

Apart from the excellent advice above, I'd also suggest you also consider the capabilities of your mount - if you aim for a pixel scale of X arc seconds/pixel then your mount needs to track at about half this value.  The other factors that will determine your lower limit will be your local seeing conditions and your scope.  Each of these factors acts as a blur which smears the details of the object of interest.  

So, for me, who's interested in high resolution DSO imaging, my lower limit appears to be around 0.7 arc seconds/pixel.   It would only make sense to decrease this target value if I went for a DSO lucky imaging approach where the aim would to decrease my average FWHM, however since this would mean quite short exposures a replacement camera would have to have a much higher QE.

Alan

47 minutes ago, Datalord said:

Thanks Alan, that's very tangible advice. I looked over my pre-stretched picture and the cores are above .9 in both lum and color. I have some narrowband I had a test with, which might work well for starfield and core, so I'll try that.

OK, I'm glad that you found that helpful.

One other item that you may wish to consider: given your pre-stretched values are very high (eg 0.9) it is likely that you're on the non-linear portion of your camera for these parts of the image.  If you examine your unstretched RGB image and you can see odd looking star colours on the very bright stars - magenta/purple is common - this is an indication that you are on the non-linear portion of your camera, a consequence is that star colours will not be accurately represented.  To correct for this, I'd suggest you experiment with the Pixinsight repair script Repaired HSV separation on the unstreached RGB image. I generally use the default values, measure the approx size of the problem stars in pixels and that insert this value into the routine.

Alan

10 hours ago, Datalord said:

Does anyone have a golden advice for me on how to get this stretched without blowing it up?

In Pixinsight if your luminosity value is greater than about 0.8 (which you can measure with the readout probe) then you will find it very difficult to get colour into that part of the image.  

If I have an object that I'm imaging then I will generally stretch the object until it has a maximum of 0.8 in the area of interest. This becomes Lum#1.  I then take a look at the lum values of the stars, and if they are very high for a lot of these eg > 0.8 then I will perform a separate new stretch which just concentrates on the star field, this will obviously be much lower - this creates result Lum#2.  I then blend the result of the both results to give me result Lum#3 which is best compromise between the two stretches. 

Although this is a matter of personal taste, I personally would not be too concerned about eliminating all stars with white cores, some stars are very bright compared to their neighbours and so to me, it is quite natural for them to look this way.   However, if you have a very bright star (with a white core) which you really don't like then I would recommend minimizing its impact through size reduction.

(If you are interested in seeing my attempt at the Iris Nebula - have a look in my album Deep Sky III) 

Alan

7 hours ago, Brian Maurer said:

Wow that really smacks you in the face,  wry nice!

Thanks for the comment.  Yes, the image doesn't really feature pastel colours very much 

Alan

Many thanks for all your comments, they are much appreciated. 

Alan

A narrow band close up of NGC 6995 with Ha mapped to red and OIII mapped to blue. An artificial green was generated by Carboni's PS actions. I decided to attempt realistic looking colours by calibrating the image via Pixinsight's Photometric Colour Calibration tool.

The result of a 30 hour integration is shown below and was taken with my Esprit 150.

Apart from the interesting detail, I found if you stare at the image you can see a variety of shapes - so far I've spotted a large horse (red), an owl (blue) and deer skull (blue).  What you can you see ?

Alan

LIGHTS: Ha:40, OIII: 20 x 1800s, DARKS:30, BIAS:100, FLATS:40 all at -20C.

14 hours ago, ollypenrice said:

Some audacious reds and blues there but if you have the signal you can flaunt it! I like the lower right part of the image best, I think, the dust having really fine modeling and the darkest parts being entirely unclipped. That's signal for you...

Olly

Thanks for the comment Olly. 

I was quite surprised about how much blue, presumably emanating from the blue reflection nebula, the object contained. In the renditions I have seen, I could only detect this weakly, so here I was attempting to emphasize its presence.  Overall, a very interesting object consisting of the emission, reflection and dark nebula - as you have pointed out above, the latter is very dark indeed.

Alan

Due to the poor UK weather I hadn't been paying much attention to how my automated imaging set up was progressing with this target. So, I was a little surprised when I discovered that it had been very slowly capturing data of this target for the past 6 months........Anyway, here's the result of 32 hours integration time of my first attempt at the Cave nebula (SH2-155). 

The LRGB image below has an Ha blend into the L and Red channels and was taken with my Esprit 150.

Alan

L: 20, R:13, G:23, B:15, x600s, Ha: 41x1800s, DARKS:30, BIAS:100, FLATS:40 all at -20C.

1 hour ago, serbiadarksky said:

How much are the galaxy images cropped? I am sure thats not the real fov as the esprit 150 doesnt have that much fl.

I don't honestly know, all I do is crop my images until I get the prettiest picture !    

In imaging, the field of view is determined by the focal length of your scope and the pixel size of your camera. To see the various FOV with a specific scope and camera and object have a look at https://astronomy.tools/calculators/field_of_view/  

The Trius SX814 gives my set up an imaging scale of about 0.7 arc seconds/pixel, which is quite a high resolution. 

Alan

20 hours ago, Seanelly said:

Further info, if possible, available upon request. Ideas, suggestions, or a solution would be greatly appreciated, as I have no idea what in Heaven's name (or Earth's) is happening here.

I've had to look at your image and in addition to the horizontal lines you have a collection of dust donuts.  To minimize these, I suggest take some flats, the most consistent and reliable method that I've found to do this is via an EL panel.  If you find flats/darks/bias a bit of mystery then I'd getting a copy of Steve Richards excellent book  "Making Every Photon Count"  - https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

You can also minimize both of these unwanted effects in PS.  The horizontal lines can be minimized by one of Noel Carboni tools called Horizontal Band noise reduction, the dust donuts via the context sensitive spot healing brush in PS. You can download Noel tools from https://www.prodigitalsoftware.com/Astronomy_Tools_For_Full_Version.html  and represent excellent value at $21.95.

Alan

1 hour ago, Saganite said:

Great images Alan , but for me The Ghost is just fantastic !

Thanks ! 

Alan

It was quite difficult for me to select five of my favorites from a productive 2018, but here they are. All are taken with my Esprit 150.

Alan

SH2-136 (Ghost Nebula)

M106

NGC1333

NGC4631

NGC4685

An excellent write up Steve. 

The only major difference from my own workflow relates to the star selection process for the PSF creation. So for me:

1.  I constrain these to be within my camera's linear region, in addition to having a minimum signal level,  so for me, the max value is about 0.6. 
2.  I never (try) to pick stars that are embedded within nebulosity since their stellar profile will most likely be contaminated by the nebulosity.  
3.  To minimize optical distortions I try to pick stars that are near the center of the frame.

After you have created a list of candidates, Adam Block's Pixinsight deconvolution tutorial advises that you should sort the Mean Absolute Deviation (MAD) column and look at the numbers.  This gives you an idea of the quality of the input data.  Apparently, what you are after is a consistent set of numbers within a factor of say x2.  If you find something outside this range then you should consider deletion of the outliers.

Alan

2017 was productive for me, I found that my transition to unguided imaging has significantly improved my imaging productivity.  Lost guide stars used to be a significant problem area - but no more.  

Anyway, here are five images from 2017, all taken with my SW Esprit 150 and a SX Trius 814.

Alan

M1

M82

M81

NGC7635

NGC6888

3 minutes ago, Pickwick said:

Hi Alan,

Thank you for a comprehensive reply, I have been using the free trial version but have got stuck on ACP weather interface for HitechAstro relying on a script to interface with ACP. How do I set out to do this any example would help.

Cheers

 

Pickwck

 

 

Hi Pickwick

Firstly, you need to ensure that you have configured the Weather server via the HitechAstro app. 

To communicate between ACP and the weather server, you need to set up the weather ID in the ACP preferences tab weather (ACP->preferences->weather). The weather ID for the HitechAstro server is HitecWeather.Weather

To connect the sensor to ACP and assuming you are not using Scheduler (which will initate the connect automatically) you then go Weather->connect.

Alan