halli

Thanks Sean

Hi All

A recent (August) 130pds image of M33 with an ASI 1600mm-c.   

The image is LRGB with the red channel enhanced with Ha

4 hours ago, Bossen said:

What a jawdropping image!! Well done!

Thanks Bossen 

I guess certain well known objects are worth revisiting with new kit or knowledge to see if they are any better than when you first tried.  

So this is M33 cropped with 130pds and Atik 383L+

Processed in PI in  LRGB about 38x600s L and 12x600s each of RGB

Hi

Had a go at IC1848 with the 130pds and Atik 383l+  .  

Around 10x1000s HA and 5x600 secs RGB

Processed in PI (HaRGB) - thinking of how to introduce HA in the red channel as well without washing the star colours out - any advice on this welcome - star mask does not appear to work !

Hi

Had a go at Pelican/NGC7000 using Narrowband and RGB now Cygnus is coming into view.

Using 130pds with Skywatcher CC and Atik 383L+

About 7x1000s Ha and 7X600s each of RGB 

I decide to combine the Ha as a luminance with the RGB - and this is what happened !

Thanks Rob - looks like some really useful info there - much appreciated !

I have used the SGP flat calibration wizard to provide the exposure for a given ADU target  figure but not sure how accurate it is though - unfortunately I do not have Maxim

I  am in the process of trying to connect a skywatcher CC to my EFW2 filter wheel.  My understanding is that the scope side of the cc is push fit into the draw tube and the other side is M48 male for the filter wheel/camera.  I believe I need a M54/M48 adapter to connect to  the EFW2 which I am struggling to source !

Not sure if I can visualize your set up with the internally mounted CC.

Is it a 12v LED display? Could you drop the voltage with a dc-dc convertor to lower the brightness further?

Interesting thought Rich yes it is 12V and therefore it is worth trying to reduce the input voltage as you suggest  -  I'll certainly look into that thanks for the idea !

I've had good results with ADUs in the range 14,000 to 30,000. I don't think that it's mega-critical as long as you are well out of the noise floor and not saturating the sensor. Flat field corrections in software are multiplictive so, in theory at least, as long as you are not clipped at the black or white ends the corrected results should be the same as long as the sensor is linear. The KAF 8300 is, apparently, quite linear and is used for scientific work.

With regards to the back focus distance, you'll have a fun time sourcing all the spacers that you'll need to get it exact. I found Telescop-Express to be a very useful resource.

The third screw in the eyepiece holder is an absolutely must with the weight of the coma corrector, filter wheel and camera hanging off of the PDS focuser if you want any kind of orthogonality at your chip! I used an M6 allen-head bolt that I have in abundance. There's plenty of metal in the eyepiece holder to take the bolt. Taps and dies are cheap and you just need to find a buddy with a pillar drill (every astronomer should have access to a pillar drill! ). You can see the bolt in this close up:

focuser.PNG

You might also consider tightening up the focuser a bit too. See here: http://www.teleskop-shop.at/testphotos/w-erbung/Crayford_adjustment_Synta_microfoc.pdf I found that the weight of the imaging gear would slowly unwind the focuser over the evening until I had "corrected" the tension in mine.

Thanks also for your response Paul.  Its good to know that the ADU value isn't so critical !   I have used the SGP flat calibration wizard which finds the exposure for  an ADU value which seems to work quite well.   The fiddly bit is dimming the light source so that the exposure values are high enough for the 383.   

Not sure what I am going to do about the third screw !   I guess I may be able to use a hand drill  - not sure .  Certainly longer bolts are needed in my case as it is difficult tightening them by hand because of the proximity of the filter wheel body.  An Allen head seems to definitely be needed when trying to hold the weight of all the gubbins.  

I was thinking whether there was a brass compression ring adaptor that could be screwed onto the end of the drawtube to replace the current assembly.  The focuser seems ok at the moment if I use the locking screw after focussing,  but thanks for the link  - Im sure that will come useful in the future at some point

Cheers

Ian

Thanks Ross. I'll try that value out.

Hi Ian,  yep its cropped, total exposure is just under an hour, 10 x 600  at 800.( modded 600d ) with a master bias and master dark. I havent carcked the lights thing yet.

Btw, v nice image too. must try for that myself.

  Thanks.  I will certainly have a go as well myself at M1.       I have a GSO RC8 so probably try that out on it as it has a longer focal length - but good to see its reasonably tolerant to cropping as it is a small object.  

You captured some nice detail  !

When taking flats with the 130, use a large lightsource (ie: a big monitor running notepad or Al's virtual lightbox), back it away by about 10 inches and diffuse the light with some copier paper - that will help prevent stray light from bypassing the primary/secondary and going straight up the drawtube.

In regard to the CC, try to stay as close to the 55mm spacing as possible as going over that will increase the reduction factor, but increase coma in the far corners. It also helps to have three thumbscrews fitted rather than the standard two, that will help prevent the CC from flapping about in the drawtube under the combined weight of your imaging train (a CC, FW and 383 is a bit heafty).

Thanks for the advice Rob.  

I have bought an A3 LED display for flats and am experimenting with this.  Because of the shutter on the 383 it means that the right amount of light reduction needs to be made to increase the exposure time -  which is a bit fiddly.  Unfortunately the panel can be dimmed but does not dim enough !  Its a question of diffusing the light enough to get to the right exposure I guess. I am also going to look at the T shirt method outdoors but again its getting the right thickness of material to get a long enough exposure !  Bring back AV DSLR flats anyday !

I believe a figure of 25-30k ADU and above 5s should be achieved  to avoid the shutter affect ?

Wrt the coma corrector yes the drawtube focusser scews arent the best and I thought of replacing the complete unit which holds the screws  as it is difficult to tighten the screws with the filter wheel in situ as it is. Haven't researched this yet though.  

From the Atik site the backfocus for the 383 is quoted as 17mm which I assume is from the chip to the 383 mating interface - I guess this is the distance I add to the EFW thickness and then add the CC internal distance to the lens and then also add a spacer if required to get 55mm     Does this sound about right to you ?

Nice crab Simmo - good size for 130pds - was it cropped ? What was the exposure length and number of lights ?

I also managed to make use of a full clear sky the other night without the moon !   I am still getting used to using a mono CCD with filters and LRGB processing so I thought I would select a cluster in this case the beehive M44 where there were some different colours in the stars.

Still mastering flats with the 383l so there were none !

6x1000s L

6x600 r,g and B

I have just got a Skywatcher Coma Corrector but haven't fitted it yet to the 130pds so there is a little coma in the cornerss of the attached even though it was cropped to get rid of the majority.

I would appreciate if any one has any advice about fitting the CC with the 383l.

I hope you like the cluster (at least the right colours appear to have emerged ...........)

Any advice/comment on the processing welcome !

Ian

Hi all

Thought id post the below from the first clear night for quite a while !  

IC405 the Flaming star nebula.  

Canon1100D modded with UHC filter and 130pds

6 x 1000s subs with flats , darks and bias

Please excuse the coma.

I have recently acquired an Atik 383l+ mono and hope to be up and running with that soon - although its a steep learning curve !

Hi Damian

Congratulations on your monster mirror - what a saga and such brilliant determination !  

I was browsing Stargazer's Lounge and decided to look at some mirror making treads and accidentally came across this one a couple of days ago !!!

I have returned to astronomy a couple of years ago after a gap of almost 30 years.  The  last thing I did all those year's ago was to make a 8.75" mirror using Texerau's book.  My deadline for the complete scope was to view Halley's comet in 1986 which I just about achieved.  I remember  using a spare bedroom and during melting some pitch the neighbours knocking at the door complaining of smelling the fumes which had entered their house by some means.   We still have a laugh about the look on their faces when I told them what I was doing  - even now !  

Nowadays I have taken the easy route and bought some kit and am into imaging.

Your thread brought back so many memories  - making a mirror is certainly a test of character.  Thank you for taking all the time to document  your experience - it is really appreciated.

I left off making mirrors after getting a 15 inch blank from Galvoptics in Essex - ready for my next project.  Sadly I never got around to grinding it and it is still lying dormant together with a glass tool and grinding grit  - didn't have enough time in those days.  

However I have more time now and retirement beckons and your endeavours were truly inspirational  to such an extent that I may well start the big grind on the 15" even though I get my kicks from imaging and not observing these days !!  I guess a Dob will always come in handy.  

I think the thing that drives mirror maker's forward is the access to large apertures and the thrill of creating a mirror yourself as good if not better than one you can buy - looking through it for the first time and bringing a star into focus is a truly wonderful experience and  there will always be a bigger mirror next time !!!!

I hope the same goes for you and thanks again for re-kindling the excitement that I felt all those years ago !!!

I look forward to your build thread and the culmination of all your good work

Best wishes

Ian

Thanks for the comment Damian and for the OAG tip Mike.  

I can see from the way the OAG is constructed that the focus is going to be fiddly !  

Unfortunately I dont have an object visible from my garden far enough away to represent the kind of focus necessary to represent a star so I may have to wait for a clear sky to work on it  which is a shame.    I have found that focus is achieved with my DSLR with the three extension rings on and the focusser just wound out about 5mm, so I have taken one of the rings off to put the OAG in so I guess I may be able to figure out where the rough focus needs to be with the DSLR beforehand.   I am hoping there may be a bit of a clearance early on tonight to have a fiddle.  Looking forward to it !

Thanks again

Ian

Hi Everyone

Well it finally arrived !   Although when unpacked it was branded TecnoSky not Altair Astro.  However it was a GSO RC8 with exactly the same spec including the Losmandy plates and 3 extension rings.  The first collimation with a Cheshire showed it was only slightly out and needed a little adjustment to the secondary only.  A further slight adjustment to the secondary was made with a star test.  Not sure how well I have done this so would welcome comments on the attached image.

So to the first real light with a camera !

I had a go at open cluster M103 to give it an easy first try  but without any guiding set up I had to reduce the exposure length to about 60s - and took 30 subs.

The result is attached after a quick and dirty processing in PI to get something out.   I am quite pleased with the star shapes as far as I can make out  - although some slight coma deep in the corners under high magnification only - which doesn't bother me !  

I would appreciate  any comments particularly at this early stage.

I have also obtained an OAG and focal reducer but want to do some work without the FR first so I can compare befoere and after.  I also  need to set up the OAG!   I presume this just goes in between the focusser and the camera.  It has a 2 inch nose piece supplied with it and I hope to use my ASI 120MC as the guide camera.  

Any tips on setting the OAG up would be most welcome !

So onward and upward to bagging some galaxies !

Best wishes

Ian

Latest update  -  found a source of the AA RC8  in Europe - AST Optics -  so i've pressed the button and ordered it !    

They despatched it on 22/7 and according to the tracking status it is now on route in 'Gran Bretagna' after travelling through 'Germania' having started its journey in Alessandria.    So it may be here very soon !    

The excitement mounts...............

Failed at he first hurdle - out of stock with AA currently - 6 weeks anticipated for new delivery................... very frustrating ! 

ok guys  - I have pressed the button and ordered an AA 8inch RC with metal tube from Rother Valley Optics today !

Let you know how I get on.

cheers  Ian

Agreed Olly experience is the key - it seems from Sara's and John's experience above that CF seems to introduce focussing issues due to temp change and not the metal tube  - if I have interpreted correctly !

More food for thought in your responses !  

I guess there  is a little twisted logic to getting a scope for a longer focal length and then using a FR - I guess the RC is probably  worth it for its compact nature and coma free optics anyway !    I guess I will try it at its native F8 and see how it behaves before fitting a FR.  

I believe the AA one has all the spacers required.  I dont see much point in going for the CF tube for just weight alone as it is an extra £300  or so and this can help fund  a better focuser.  

Lovely galaxy images John - there appears to be a whole new world of DSOs on offer with this scope !

Ok having seen what is possible with this scope  - I am up for the challenge ! -  and aim to get the ALtair Astro 8 inch.  Although am tempted by the 10 inch but the cost is another £1000 !  

Any views in whether this is worth the investment ? Have a NEQ6 so  should be ok.  

Many thanks for all the contributors to this thread and in particular Johnrt who has proven that the scope can be taken to a workable device which takes great images of small DSO.  This has helped consolidate my view although it may be a rocky ride !

I have a 130pds for widefield and want to hop on to an evolutionary path to more aperture and focal length for smaller objects - only have a DSLR at the moment  so am hoping that this will be OK at F8 wrt S/N.  However the end point is  CCD but a little later and I guess a focal reducer will bring the Focal ratio to a manageable state.  

Has anyone any views on the best FR to use ?

Thanks in anticipation.

Ian

These are lovely images with nice colours

They almost undermine the benefit of guiding  !

I always thought that the aim was to take as long an exposure as possible to reveal the finer detail ,  however you have revealed a lot of detail  with a large number of smaller exposures.

 I guess there is a limit as to when adding more exposures reveals anything further and the potential to reveal faint detail is greater with longer exposures.   However long exposures require good tracking and delicate setting of ISO levels so as not to over expose especially in light polluted areas.  This results in more bad subs during an imaging session.

The simplicity of shorter exposures cannot be underestimated in the light of these results !

Lovely image !

Congrats on taking the plunge and going Narrowband. I've just hit the second stage in the prcess by modding my DSLR and using a UHC filter to cut down light pollution. Just trying the modded camera out tonight. Started with a few subs of the California neb to test out the Ha gathering capability and am currently imaging M101. Yet to process these.

Look forward to see your finished Elephants trunk - looks like a very good start - it must be quite exciting producing CCD images for the firsdt time ! The amount of detail revealed is amazing. Great to see you can use the technique to defeat moonshine - that really increases the time available to image DSOs ! Great way to fight the dreaded light pollution as well. Only disadvantage I guess is the length of time spent imaging by adding in the different wavelengths over a number of sessions. I use Astrotortilla to keep targets central although there must be an easy way of getting the camera in the same position every time to avoid too much cropping when stacking !

I feel I need to muck about some more to drag out the last dregs of performance from my DSLR now I've had it modded before I feel I would be ready to get a CCD - although hopefully not too long !

Cheers