Albastars

3 hours ago, Clarkey said:

I recently purchased the Starwave 115mm and I have been impressed with the optics. In theory the FPL53 in the Wave should be better, but I have not noticed any false colour with the Starwave which I believe is FPL51 - although I don't think it is quoted in the sales blurb. Overall, it seems pretty well made and good value for money. The only negative for me is the focuser is not as good as some. It is certainly useable, but there is a small amount of play in one axis. Using spacers, I am keeping the focuser racked in as far as possible to eliminate it - but I will probably get a replacement at some point. The dew shield was also slightly loose, but this was easily rectified by adjustment of the tension screws. I would suggest that the TS-photoline version is virtually identical optically and from experience their focusers can suffer from some movement too. For info, I have been using the standard Stella Lyra FF as I already had one and it works pretty well and saved a few ££'s over the 'official' one.

StellaMira 2" Field Flattener with M48 Adapter | First Light Optics

Have you considered a Ritchey-Cretien? Can be a bit tricky to collimate initially, but once dialled in they do not really move. Good value for aperture and FL. You would probably need a replacement focuser and a FF (for the RC6) - but still a lot of bang-for-your-buck.

HTHs.

Thanks @Clarkey , that's really useful.  I was wondering about the quality of the focusers.  It is a larger focuser on the Wave 115mm but I guess that doesn't necessarily mean its of a good quality.  I think the Starwave is at the top of my list and if I need to upgrade the focuser, I can afford it.  I will keep in mind the StellaMira FF, its looks a good option..

Ritchey-Cretien?  Well, I hadn't considered them at all.  More research needed!

Cheers

I have around £2000 to spend on a new telescope and need some help choosing.  

It’s for imaging DSOs only on a Zwo AM5 mount. Presently, I have a WO Z73 and I’m using a modded Canon 800D but am looking at upgrading to a Zwo ASI2600 in the near future. 

I prefer a refractor over a reflector. I’m looking for as long a focal length as I can but I think up to 800mm is affordable and within my mount’s capabilities. I guess I will need a 1x Flattener too. 

I’ve found a few 115/f7 scopes including - 

Ts-Optics Photoline - £1299

Altair Starwave - £1299

Altair Wave - £1899

Starfield Gear115 (from FLO) -£2098

The cheaper ones appeal obviously but will I have to spend on upgrades?

Do any of these scopes stand out as the best or are there alternatives, perhaps longer options? 

If anyone wants to suggest a reflector my main worries are its size for transportation, repeated colimation and the need to upgrade parts and fettle. Open to persuasion though - I was looking at the Vixen R200SS.

Thanks

That is stunning!  Thanks for posting.

On 26/01/2022 at 14:11, Elp said:

@Albastars Thanks that link was great.

There was the highlighted point "Very important to remember. When you do your flats at different ISO than your Lights, you have to calibrate your Flats with matched ISO dark-flats or BIAS frames !!! Keep that always in mind."

Haven't done this myself, can it be done in DSS?

Sorry @Elp I don't use DSS.

On 23/01/2022 at 19:31, david_taurus83 said:

I aim for around 2 seconds with my 6D. The problem with the on camera histogram and APT one is they both measure the 8 bit jpeg yet we work with raw files. I use NINA and expose to around 8000 ADU, half of 14 bit Canon 6D max ADU value. On the camera, this is why over on the right edge of the histogram but they work well.

Similar for me with a modded Canon 800D.  I came across this article a while back and found it useful - https://www.myastroscience.com/proper-flats-with-dslr

Thanks @ONIKKINEN and @Clarkey 

If it is tilt, I guess its a fraction of a millimetre?  I don't think I have room to fit a tilt adjuster but maybe some copper tape in the right place might help.

The weather for the next week is grim, so I'm going to have to be patient.

Thanks again.

Hi,

Can anyone tell me what might be going on with my star shapes?  I think possibly I need to increase my back focus a bit but the corners are not uniform.  Perhaps some kind of tilt in there as well?

One debayered sub (180secs) attached.  Ca\non 800D, WO Z73ZS scope with WO 0.8 reducer with adjustable back focus set to recommended 1.8mm - total BF of 56.8mm.

Thanks

Dave

I saw a great picture by Adam Block and was inspired to have a go at Orion.  A year ago I thought the night sky was just stars, I had no idea about anything else!

• Canon 800D (modded), Canon 40mm
• Fornax Lighttrack II
• Bortle 3
• ISO 400, F4, 82 x 2min subs - 2hrs 44min integration.  
• Processed in PixInsight

I would have liked longer but the clouds rolled in.

I'm not sure if this is the finished image yet but here it is anyway.

23 hours ago, AstroMuni said:

It looks great. If you cropped the image and then did your stretching I reckon it would turn out a lot better. And as you said, adding calbration frames should help. Wouldnt have guessed that its from compressed jpg images.

I have taken the liberty to quickly process your image from above in Siril and here is what it looks like So I am sure you can get a lot more from your original one. So all in all not wasted effeort in my beginners opinion. I would have been chuffed if I got anything like this. Good luck.

I'm impressed, there is a lot hiding in that jpg.  Thanks for taking a look. 

Rather than work on it though, I got another 4+hrs on the Pacman, this time in RAW.  This is my processing so far but I've blown the big stars in the nebula - I'm learning about processing all the time, so I'll probably go back to it.

On 09/12/2021 at 09:56, AstroMuni said:

Would be interesting to see what you have managed to capture. It might not be as bad as you think.

FWIW, this is just registered, stacked and auto stretched with no calibration frames.  I guess if I worked on it there might be a reasonable image in there somewhere.

But moving on, I was out last night and hopefully got 5 hours on the Pacman.  Thats my third attempt in 10 days - the first try was ruined by gusting winds.

I had this odd feeling through the night that something was wrong after a rushed set up.  Just collected 6 1/2 hours of what appears at first glance to be good data - except its all in jpgs 😖

Ah well, onwards and upwards.

14 hours ago, ollypenrice said:

...  and then went into Image-Adjustments-Selective Colour and greatly lowered the cyans in red. This two-second trick is simply astonishing for getting more out of Ha signal buried in one shot colour data.

Wow, that brilliant!  I don't have PS but I can do it in Affinity Photo.  Amazing.

11 hours ago, Robculm said:

Fantastic result & a great use of a clear moonlight night! Here's me wasting the night just optimising guide settings & wondering why there always seem to be more clear nights when the moon is up?!?!

Can I ask if you bought your 800D modded or where you had it done? I'm contemplating the same for mine, just a little worried about comments I've seen regarding 'star bloating' on modded cameras... But would love to get a little more Ha...

Thanks.

I had used my Sony A7Riii for a few images before I bit the bullet and bought a used and modded 800D from Andy Ellis of http://astronomiser.co.uk/ .  Andy provided a quick and efficient service and all good with the camera so far.  Because I've no before and after experience with the modded camera I can't really comment on star bloating.  

14 hours ago, ollypenrice said:

That's great. Well done. To take it further I'd be looking at two issues, reducing star size and getting more Ha signal from the existing data.  Just working with a screen grab in JPEG (so a terrible way to work!) I took the image into Photoshop and ran three iterations of Pro Digital Astronomy Tools (AKA Noel's Actions) 'Make Stars Smaller' and then went into Image-Adjustments-Selective Colour and greatly lowered the cyans in red. This two-second trick is simply astonishing for getting more out of Ha signal buried in one shot colour data. I would not use these methods, or not so heavily, if working from scratch because there are more subtle and more complex ways of getting there. However, my aim wuld remain smaller stars and more Ha. I think your capture was very impressive.

Olly

Thanks Olly, I'm new to astrophotography (but not photography) and had tried to reduce the stars but I was getting too many artifacts.  I use a star de-emphasiszer script in PixInsight based on work by Adam Block.  I rewatched some videos and played with the settings a bit more and got a better result but perhaps not as strong an affect as yours. 

Re Image-Adjustments-Selective Colour in PS.  Can the same be done in PI?  In this version I increased the reds in curves using a colour mask.

There is so much to learn that its daunting and fascinating in equal measure!

I took this on the night of the last full moon and had low expectations for the result - just out for practice really.  Its not the best but I'm very, very happy with it.

• Canon 800D -modded, WO Z73 with 0.8 reducer (344mm)
• Lightrack II mount
• ISO 200
• 90 x 3min subs
• 30 each of darks, bias and flats
• Processed in PixInsight

Suggestions to improve it are very welcome.

Thanks everyone.  I have lots of options now!

@Grant93 Red dot finder.  

@alacant When you get close to your target, lose live view and take single, say 5s, frames at ISO12800 so you can see any nebulosity and frame properly.

@Tomatobro I plate solve until the declination matches the object and then adjust the RA. Adjusting both at the same time does not work for me.

@Tiny Clanger Cheap 50% solution (i.e., gets the alt sorted, you pan for the az) get a simple electronic level (they cost around £15 ,  are powered by a couple of AAA cells,) Find the alt of your target with whatever ap  or program you like, put the level on the tube, elevate it to match.

@Tiny Clanger'Push to' with SkyEye.  

@Spile I had to look up asterisms!  Right Angle Finder.

All good suggestions, thanks.  And not expensive solutions either.  I'll give them all a try.

Re the SkyEye app.  Its Android only but I searched for something similar for iPhones and it seems I already have something installed - Polar Scope Align Pro.  I need to find or make a phone mount/cradle to get this one to work but it does look promising.

I get lost sometimes trying to find targets.  I can find constellations by eye and the bigger stars in my scope and then star hop towards the right area.  Then it gets difficult sometimes.  I've tried twice to find the Soul Nebula and failed - the area between Cassiopeia and the Heart and Soul nebulae seems really dark.  Being on hands and knees plus twisting my neck to see live view doesn't help either.

I'm viewing/imaging with a WO ZS73mm (FL 430mm or 344mm with reducer) and live view on a Canon 800D.  I use  SkySafari as a star map.  I have a Fornax Lightrack mount and can move the Dec and RA independently.

Get a Go-to mount is the obvious answer but I'm not ready for that yet.  I can blind plate solve with Sharpcap but its very slow and often fails to solve  (PA works amazingly) - I need more practice and to tweak the settings I guess

Am I missing something?  Some bit of hardware or software?  A red dot finder would help with the initial navigation but with finding an invisible target?

Thanks.

Thanks Wim and City9Town0.  I tried arcsinh initially but it didn't work for me - I was a bit too aggressive I think.  On seeing Wim's processing (thanks for taking the time) I gave it another go and got a better result.

Great info Wim about the differences between scopes.  It would seem some of my problems are due to my expectations!

For my own curiosity I'll try again but with a shorter exposure time.

Thanks again.

I'm a newbie at this and, as recommended in another thread, I tried a star cluster just after full moon last week.

I imaged Caroline's Rose - NGC 7789 last week with the moon at 62%.

• Canon 800D - modded but not full spectrum
• WO Z73ZS (430mm)
• 4hrs integration (120 x 120secs) plus 30 bias, 30 darks and 30 flats
• ISO 200

I usually expose for nebulae at ISO 400 and 3 min subs but went with the above to prevent blowing out the stars.  That didn't work too well it seems.

I've tried Photometric Colour Calibration and the Repaired HSV Separation script that I have seen recommended but I cannot get colour back in the stars.  After sorting the background and gradient plus a bit of deconvolution I'm happy enough with the image - it just lacks colour!  A stacked and cropped (no other processing) xisf file is attached if anyone has the time/inclination to look at it. Can this image be rescued?

 Re the exposure:  I found this lovely pic on Astrobin - https://www.astrobin.com/ey3xlq/ - 30sec subs at ISO 800.  Are 120secs too long no matter what the ISO?

2BREF_crop.xisf

3 hours ago, vlaiv said:

Planck's law is given by this formula:

And it only uses one variable - T or temperature (other is frequency and we are interested in range ~ between 400 and 700 nm) - all other things are constants - e : base of natural logarithm, h : Planck's constant, Kb : Boltzmann's constant and c : speed of light.

It produces distinct spectrum for each temperature. Other unknown is integration time (multiplicative constant).

In principle you need only to measure graph in two points to be able to solve it for temperature.

Once you have temperature - you have color of the star:

 

😱 Well, I did ask.  More years ago than I care to remember I scraped a Grade C Pass in maths. That is the stuff of nightmares for me! 

Thanks for explaining though vlaiv.

Thanks vlaiv and Colm.  Great info and tips there.  

I think I'll hold on the filter for now (maybe keep a look out for a bargain on the L-Enhance) and I'll read up on quad band filters.  I will take a look at star clusters - you are right Colm, I could do with more practice, lots of it!

5 hours ago, vlaiv said:

or alternatively - do some really clever math to get star color from filtered data.

Are you meaning Photometric Colour Calibration there vlaiv?

This months full moon coincided with a lovely clear night and this got me thinking.  Is there a filter that can help counter the effects of moonlight as well as light pollution?  TBH I'm doubtful because moonlight is broadband, right?  But I've read that the Baader Neodymium filter can help - reports seem to vary.

Here's my set up/situation:

• Modded (not full spectrum) Canon 800D
• WO ZS73 scope with flatteners, both the x1 and x0.8
• Fornax Lightrack mount (3 min unguided subs with the above are OK to my eyes)
• Have Bortle 4/5 skies.  North and east of me I have B4.  To the south and west I have B5.
• I'm targeting emission nebulae and the large galaxies at the moment and I want to preserve star colour as much as possible.

In my limited experience I haven't found light pollution to be a problem so far.  However, my research so far is suggesting the Baader Neodymium, the Optolong L-Enhance and the Optolong L-Pro might help.

I guess that the L-Extreme filter is the best option but I don't think I can achieve long enough subs.

Any suggestions?  

On 25/07/2021 at 13:47, BrendanC said:

Finally finished this - a four-pane mosaic going from the North America Nebula across to the Pelican Nebula. Culmination of the past 8 clear nights, and literally hours and hours of trying to  get it to work. I've never done a mosaic of a nebula before and it was a very steep learning curve (yes, another one).
* 17:39 hours of integration at ISO800 from 120x120s + 37x180s + 177x240s subs, over 8 nights
* Bortle 4 sky, Moon average 60% phase, 27° height
* Calibration: 25 flats, 25 dark flats, 50 darks
* Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher NEQ6 mount, Canon EOS1000D DSLR camera with IR filter removed, Sky-Watcher 0.9x coma corrector, Datyson T7C guide camera, Angel Eyes 50mm guide scope
* Software: Polar alignment with SharpCap Pro, guiding with PHD2, capture with Astrophotography Tool (APT), stacking with Deep Sky Stacker (DSS), post-processing with StarTools, Photoshop CS2, Affinity Photo and Topaz Denoise AI

Wow!  I think that's gorgeous.  

I managed 3 1/2 hours on the Pelican Nebular a couple of nights ago.  I think its my best image yet.

Processing in PixInsight, the first image is a straightforward stretch plus curves.  For the second, I split the channels and played around (I saw some techniques for OSC narrowband Hubble-like colours).  Stars were diminished on both.  Colour wise, I guess the first is the most accurate but I like the second one best.

Canon 800D modded, WO 72ZS

Fornax Lightrack II

3 1/2 hrs (68 x 185sec subs)

40 Darks, 30 Flats, 37 Biases

Bortle 5, but looking towards B4

I got this to work last night.  Just as described in the CN thread.