bomberbaz

15 hours ago, RyanL said:

Hi

Thanks for all the advice. I've decided that as the scope doesn't get great reviews I'm not going to get any upgrades, instead I'll put money into my new scope fund and just use what came with it.

At the price I paid it doesn't matter if I break it so I can use it to practice collamation and getting used to an Eq mount etc.. Just need to find some time and a clear sky to use it now.

Cheers

Ryan.

 

 

 

What a very sensible man you are and refreshing to see such a pragmatic approach.  

Should get this well with the 14" dob and I am also going to have a go at getting its spectra with the portable imaging rig.  These are exciting times. 

I use the sw az gti in eq mode with a sw 72ED. It isn't a triplet granted, but it does give a well corrected, flat field when in use with the stellamira FF and is only 2kg. However I have 2kg of counterweight to contend with too. 

The william optics range al;ways seem highly recomended and the 81mm triplet weighs in at 3.3kg. Ttoal weight is 4.5kg. William Optics GT81 WIFD Apochromatic Refractor | First Light Optics

On 12/05/2023 at 16:54, Mike Q said:

I say find a astro club and take your scope to them once or twice.  They can teach you the ins and outs about your scope with your scope.  For me it was far easier to learn collimation that way then off of a video. 

Mike makes a very good point. 

It's all well and good us lot on this thread pointing out that we use this and prefer that, but you are who you are and what suits you may be totally different to us.

Find a local club, ask to go around and you will be welcomed with open arms. 

Take a list of questions with you and you will find the answers, as well as a demonstration where practical of these answers EG collimation.

1 hour ago, Coco said:

No, VAT PAID! Price includes VAT 👍 thanks again Steve 👍👍

Blooming heck, those were a flipping bargain then, good buy!

3 hours ago, Coco said:

Treated myself while they have 40% off! thanks to @bomberbaz  for the heads up.

Astroshop.eu 

Looking through them shows no CA, razor sharp, pair of Magpies 50yrds plumage on black and white again no CA.

Clear skies tonight too... 😊

 

They look very nice Guy, was there any extra duty when they reached UK?

1 hour ago, John said:

Thanks Jeremy. My next intended target with the 100mm last night was going to be the quasar in Virgo 3C 273 which is mag 12.9 but the clouds spoiled the fun. 

Be interested how you get on with that John. I would also be interested in hearing your finding process for it.

I have had it once using the dob, but that has DSC so that's relatively easy in comparison.

Interesting video, good job he threw in his caveats at the beginning or I would be shouting at the screen 🤣

Yes his "there is tele view and the rest" comment could have grated me a little. There are some dam good competitors out there, however since I now sold my Nikon glass it is a less contentious comment  but I still don't agree with him😉

Where I think I am tending to agree is the use of two eyepiece in a session.  If I am galaxy hunting, I use one, an APM zoom. Nebula, an APM UFF 24mm. Planets, a zoom and another zoom. Then I have a panoptic 27mm for everything not covered with those 3!

If you look in my signature, the statement in white has nearly been achieved 👍

On 23/04/2023 at 18:59, vlaiv said:

There probably is not, but ASI Air is aware that you are using OSC camera and can choose bin method based on that.

Only thing that you can do is select - bin x2, and it will apply appropriate bin method based on whether it detected an OSC camera or not.

Thanks for your help in this thread vlaiv. I have been over this and other matters since but I think I am now getting a better understanding of how these things work. Sometimes they seem counter intuitive but when you thinnnk it through, it makes sense. 

Few things, Ref collimation mentioned above, get yourself a concenter. They have come down in price recently and are the easiest thing ever to use. Do watch video to see how someone does it who it skilled for tips.

If you get frustrated with your eyepiece, buy a zoom. The 21-7.2 by OVL is a cracker and will easily keep you going until you gain more experience.

Stellarium is a great tool for using whilst at the scope, Skysafari 6 plus is what I use and both are basically virtual maps of the night sky. Both can be put on dark mode and this can be used as an interactive map at the eyepiece. 

Go for easy objects at first as mentioned above. Search through stellarium for messier objects (M82 as an example) as these tend to be the easier things to find.

Most of all your a young chap, take your time learning, stars are going nowhere.

5 hours ago, han59 said:

Hi Steve,

There are two type files. 1) Files already in colour and 2) RAW colour files still in a mono format. See below.

 

1) Colour files which show already contain the image in the three base colours, red, green and blue (the image is debayered).  The same information you find in a jpeg file. 

To convert this type to mono, load the file in ASTAP and then use the viewer pull down menu TOOLS, "Convert to mono (ctrl+M)"

Example raw:

 

Converted to colour (without smooth):

 

Converted to mono

 

Now again but just normalise the RAW file:

2) RAW OSC camera files. These file from an OSC=One Shot Colour camera are not converted to colour yet. They have pixels  which by filter are only sensitive to red, or green or blue. Often in a Bayer matrix  

These RWA files are still mono but the best way to use them is to equalize the  red, green and blue sensitive pixels. This is what I call normalise.  It adjust the levels such that the mean red, green, green and blue levels are the same assumiing the light received is about white.   By doing so it eliminates the typical checker pattern.  Note that this option  has moved to the pixelmath tab in the latestes ASTAP version.

 

Example the raw again. The checker pattern is visible (for some cameras it is worse):

 

Now the raw normalised. Note the sharper stars. The noise pattern is cleaner. This is the best way to use a colour camera as if it is a mono camera:

 

You could also bin2x2 the raw image but you will loose resolution. So do this only if the image is oversampled:

 

In the latest ASTAP the normalise menu option has been moved from tab "stack method" to tab "pixel math 2" (CTRL+A). It normalises the RAW image in the viewer. This by making the mean value of RGGB sensitive pixels the same:

 

 

 

Han

 

 

Thank you very much indeed @han59 for this. I shall give this a go and see if it achieves what I am aiming to do. 

Noob question again. If, after I remove the checker pattern I then convert the RAW files to FITS say using PIPP, what will I get out assuming I don't tick any debayer options in the programme. I assume B&W.

cheerrs

steve

2 minutes ago, Elp said:

You need to decide what you want to see first, no point getting one scope then realising its focal length is too long or short.

A very important point that I overlooked. If you are planets only person as an example, then a dob may not be the best option. 

I overlooked this simply because although I view planets, but they are not my main thjing to view.

8 minutes ago, nikooo said:

Ok, thank you. So would you say for that money difference It's a good deal to buy 250, even If I'm new in the whole this telescope world

@Spile alludes to the fact a 200 suits him, it meets his needs and that is what matters. And that is what you want to consider.

Right now, with my own preferences and experiences a 250 would be my option on a set budget, but that is based upon what I know and what would suit me, that is as clear as I can be as it's not my money and I am not you.  

Balance up what people say and their experience then you have to make an informed decision.

Either way, 200 or 250, neither will be disappointing.

5 minutes ago, nikooo said:

Hi, this is the first time I'm actually buying a telescope, so I'm an amateur. 

I was looking to buy a Dobsonian telescope, but I don't really know which of these should I buy... a 200/1200 or the 250/1200. I mean I saved some money and right now I don't know If I should pay more money for 250p because I don't know How big is difference between 200p and 250p.

 

Let's say that I want to save money so which one do you guys recommend?

 

 

 

A lot to consider but the biggest consideration from my own experience is portability.  If you are able bodied, you will have no problem with either but it needs considering. A 250 is about 30% heavier than a 200.

If you are able bodied, are comfortable with the weight and lunking around then a 250 will serve you for very many years (subject to you not getting afflicted with aperture fever)

However there is nothing wrong with the 200 and the F6 focal ratio  is more forgiving on lower cost eyepieces and as far as I can gather many people stick with these for life, they are the bast selling size of dobsonian.  FYI most 250 are F4.8 - F5.

As far as aperture goes, in urban skies the difference will be negligible. However in dark rural skies, the extra light gathering power of a 250 over a 200 (about 50%) will really tell when it comes to hunting for feint fuzzies and things like globular clusters will take on a whole new dimension. Again there is nothing wrong with the 200 size. 

As far as brands goes, I really like the stellalyra dobs. dual speed focuser, cooling fan, RACI finder, roller bearing azimuth and what appears a decent alt fitting.  However the SW, ursa major and bresser all bring something of their own to the party.

I got a pair of the 8.8mm ones for my giant bins and them had to return them, the kidney beaning was horrendous.  TBF I have not really got anything else to compare too so maybe other versions would have given the same result.

I wasn't impressed with the response I got when I asked to return due to kidney beaning, not very professional in that instance although again in the past when I used them they have been fine. (off day I guess)

I saw these this morning https://www.astroshop.eu/instruments/omegon-binoculars-brightsky-22x70-90d/p,61489

They are not really hand held but the price states vat included. If this is the case, they are an absolute bargain.

For anyone interested I eventually went for the askar, the price and shootout results made it a compelling buy. If they ever bring out a 1.25 ultimate, I would be tempted.

On 03/05/2023 at 22:27, RobertI said:

I have an OIII and a UHC, I believe the OIII works well on the Crescent? As far as the 38mm 2” eyepiece goes, I recall that I found it would not focus with the reducer, so that combination is out. I’ve tried the C8 with a 21mm eyepiece plus reducer, but I now have a 24mm too, which I could try, but I suspect the 32mm will give the jump I need in exit pupil size to make a difference on the Crescent. I will give it ago this summer! 
 

Sorry to the OP for diverting the thread, but hopefully of interest.  

The 21 and 25mm will be ok for UHC as typically they are still useful down to an exit pupil of 2mm and sometimes less on very bright objects, the crescent does respond to UHC as well as OIII but when I tried both on it, the OIII won. (Both were at 5mm EP)

The OIII is not restricted to 5mm exit pupil but my testing just showed that it responded best to one of that size. FYI I could not see the crescent in my dob at 3.5mm EP, that's the difference.

A 32mm plossl in FLO'S AE  range is 29 quid, bargain. And it still give your C8 plus reducer a very nice 1.27 degrees true field of view, big enough for most DSO nebula. I think that would cover nearly all your bases and as remarked, won't bust your bank either. Let me know how you get on as I would be interested to hear about it!

Also apologies to OP, all useful stuff this though.

3 hours ago, RobertI said:

Thanks for your help Steve, appreciated. I hadn’t really considered the exit pupil aspect, that’s a good thought. I have always worked on the basis that I didn’t really want to go below 68 degrees FOV which limits me to a 24mm eyepiece in an SCT, but what I didn’t really consider is the limitation on the exit pupil. Your excellent suggestion of a 32mm Plossl gets around that, at the cost of a narrower field of view of course. And I do have a 0.63 reducer which I use most of the time. Before I rush out and buy a 32mm Plossl, do you think my 38mm 2” eyepiece might also work? There will be vignetting at the edges but I’m assuming the central 50 degrees will be no worse than a Plossl?

I( would suggest trying it. The exit pupil is a little on the large size at 5.7mm, but try that on a dim nebula, (M57 etc are far too bright) and also an eyepiece around the 25mm range to see what results you yield. I would expect the 38mm to be brighter than the 25 but the darker background would help the smaller exit pupil.  It could possibly a little washed out depending on your eyes response to darkness, none of us are the same.

What filters do you use/have?

On 29/12/2022 at 09:42, RobertI said:

Interesting to hear that Steve, I have always struggled with this one in my largest scope (8” SCT), never clearly seen the crescent shape, although I’ve never tried from a dark sky. Do you think my 8” in a dark sky would be able to show it clearly? 

Sorry Rob but I have only just seen your query directed at me from the end of last year.  I think the reason you are struggling with seeing this object is your exit pupil although you don't state any viewing details, let me elaborate.

My dob may be a light bucket in comparison but the key here is the focal ratio. At F4.86, a 24mm eyepiece gives a near 5mm exit pupil (24/4.86) so all that lovely light we need is spread over as many receptors as possible, 5mm is seen as something of a perfect size when using a line filter, OIII in this instance.  Also my magnification is 71

Now let's look at your F10 SCT, generally used for planetary work and star clusters etc. A 25mm eyepiece is going to give you around x85 magnification but the exit pupil is only going to be 2.5mm! (25/10) There in lies the problem.

Just to elaborate on this a 2.5mm exit pupil cover and area of 0.04909 cm2 and a 5mm exit pupil covers 0.19635 cm2 which is 4 times greater. You don't need to be a rocket scientist to figure which will give best views on feint fuzzies.

However a way around this is to use a reducer  Celestron f6.3 Focal Reducer | First Light Optics and you have a scope that should perform pretty well on nebula and galaxy. Pop a 32mm plossl or similar in that and presto, 40x magnification and more importantly, a 5mm exit pupil. 

1 hour ago, JeremyS said:

What are you using to get the spectrum? Can you, for example, use a Star Analyser filter/grating. 

That is indeed what I used Jeremy Paton Hawksley Star Analyser 100 | First Light Optics and I have purchased the Rspec analytical software to go with it.  For a couple of hundred quid outlay, there is a lot of fun and learning to be had.

Knowing me I end up buying a slit version but I have lots to learn before I go down that path. 

PM me if you want any more information although I will be starting a thread on my experiences shortly in the science section, just need another nights worth of data to cover off my research. 🙃

Steve

Last year I bought the eVscope from unistellar, they had a promotion on at the time and I took advantage of it. 

I have shown/shared the results with a few people in the family and they were very impressed by them.  The Tarazed below and NGC925 are far from my best efforts but I cannot find the rest, think they are on the tablet. However they give a taste of what you get. 

What I personally find more impressive to me are the results I am getting from it for spectroscopy. My interest in this subject being recently renewed after seeing a facebook post regarding the subject. It allows me to get involved in the science behind the hobby in a more meaningful way. The result below is of Talitha in UMajor.

The thing with the evscope is it is a reflector so the image is clean for spectroscopy purposes although the colour camera does affect results a little.  However I am involved with other members of the spectroscopy community and looking at workarounds/solutions to this. Exciting times.

28 minutes ago, Elp said:

Synthetic flats are exactly that, synthetic, artificial, made independent of your imaging session.

It is a similar process to that I detailed for you here:

You only need steps 1, 2 and 7 though (keep the stars) and modify like so.

Step 2: instead of painting the targets you want to keep black, paint over them with the clone stamp tool being careful to sample regions around the target similar to the background colour/intensity around your targets. So when clone stamped it kind of looks like there was nothing there where your target was (ie seamless). It doesn't have to be perfect but it helps if you take a little care.

Modified step 3: once your targets are clone stamped out goto filters > noise > median and choose value around 100 pixels, it will look like its kind of blurring out the image but you'll still see blotches where bright areas were.

Modified step 4: goto filters > blur > Gaussian blur and apply around 100 pixels again. You might need to adjust this so the image isn't posterised (hard steps between changes in colour levels leaving harsh edge steps between the changes like an ordinance survey map with its lines between changes in elevation).

Now apply the original step 7 "apply image" with the subtraction option.

Synthetic flat now applied.

Its not perfect as you can see from the stretched histogram image 2 above there's still a ring around the target, sometimes you can apply it more than once by doing the process a second time via your applied first synth flat image. Sometimes the results are a bit rough. Sometimes it doesn't work. But it's a useful technique to know. You normally have to do this after background extraction I find too when it hasn't quite worked.

Thank you for this. I remember the walking noise post now, think I started but got lost and gave up.  Then forgot about it, the last bit is an age thing.

Anyway, now I have more experience I shall have another bash. 

I recently purchased a APM super zoom, 67/68 degrees from 15.5 through to 7.7. I also have a APM 24 -65 degree and a panoptic 27 -68 degree + a 20mm plossl.

I have got rid of 2x 82 degree ep's and my beloved 102 degree Nikons plus a plethora of other glass. God that hurt letting the Nikons go but they simply were not getting the use they deserved.

I now have nothing over 68 degree fov consisting of 4x zooms and 3 fixed length eyepieces.  At one time I owned around 25 fixed length eyepiece and no zooms.

Seems a few of us are changing our glass outlook. 

Finally an apology to FLO whose glass sales must have plummeted 😆 

53 minutes ago, Elp said:

Hopefully you've sorted the issue. Sometimes such things can happen usually if the flats are overcorrecting because their dark bias signal (also incuded within dark flats) has not been removed correctly, I still struggle with them sometimes. Your data however can be salvaged somewhat with synthetic flats, below is just a demonstration of your original RGB images 1 and 2 above, how they look in Siril with a Histogram stretch preview, and after synthetic flats have been applied. The process isn't perfect but it sometimes helps with problematic data in the absence of correct calibration frames, I get it a lot with Lextreme data.

 

What did you do to achieve that, the third recovery was half decent, would be even better with more data.  Do you have any links to the process or methodolgy. I have never used synthetic flats (or even heard of them to be honest)