Firstlight for RC.. Shame it didn't last long..

[AlexN]

Well the sky was brilliant, its just a shame that the dew set it very heavily and started to dampen my spirits so to speak..

Anyway, before it got too rough, i managed a few quick shots... Nothing fantastic here, exposures had to be kept short to avoid the full moon from completely washing them out..

Images taken with:
8" F/8 RC
SBIG ST-9E
EQ6 pro

Cent A
8x1min

M8
20x30sec (subs had to be 30 sec, otherwise the stars near the core would bloom big time, and who can be bothered processing that out :D)

M16 (I've been dying to image this as I missed it last year...)
20x2min
(self guided through 13nm Ha filter)

As I said, they are nothing flash, but hey, First light of the RC went well, Its my first new data since the 28th of Feb, which all in all makes it an enjoyable night...

Cheers for looking.
Alex.

[Gargoyle_Steve]

G'day Alex, glad to see you've finally had a chance to try the RC out.
As you say early days but those images sure look promising mate, as you say with a ful moon overhead too. I hope you get plenty of opportunity to get the best out of that scope in the weeks ahead.

[Leonardo70]

Welcome to the Rc GSO world Alex...

Leonardo
:D

[Dennis]

Hi Alex

Congratulations of these 1st light images – M16 is my favourite and they certainly all look very promising.

Cheers

Dennis

[Alchemy]

nice start, how did your scope perform in the wet, did you use dew heaters or did she perform flawlessly without them.

clive.

[sheeny]

Cool! Looks like it has potential!

Al.

[Tandum]

Good to see you got it all going Alex.

[dpastern]

Good stuff Alex, getting there.

Dave

[vash]

I bet there was a big grin on your face when you typed that.

other than that I would love to see what this thing could do in good conditions.

[AlexN]

Thanks for the comments guys...

Clive : The secondary collected dew like there was no tomorrow, Im going to have to make a dewshield for it, and if that doesnt work, then im going to work on a way of heating the secondary.. The primary stayed clear as a bell.. By 1am this morning, im sure the neighbors were sick and tired of hearing the hair dryer! :)

Ashley : Yep... Even the grin on my face when looking at the rig after it was all set up was pretty big! Just looking at it thinking.. Carbon fibre RC telescope with self guided SBIG camera... Joy!!

All the images could definitely do with more exposure, and preferably not imaging through a celestial fish bowl :D

Dennis : M16 is my favorite too.. Im sure I can improve it with longer subs and more of them... I think I'll move to a 7nm Ha and an external guiding setup as self guiding through the 13nm was a little difficult and troublesom at times..

Alex.

[bluescope]

" im sure the neighbors were sick and tired of hearing the hair dryer! "

So you got the hair dryer out ay Alex ;) ... looks like you had fun ... I'm surprised at the shortness of your subs ... you culd have got a lot more out of your setup with several minute subs at least ... there's always next time.

:thumbsup:

[AlexN]

Steve: The subs were kept short due to the moon, as for the M16 subs being only two minutes, that was to avoid blooming on the stars.. The ST9E is VERY sensitive in that respect.. Not withstanding the scope being F/8, i could clearly make out the pillars in a 3 second sub.. could easily make out the dust lane in Cent A in 1sec... Its QE is the 2nd highest of all the SBIG ST series cameras, and due to it being NABG, it very quickly blooms on brighter stars... I think with a 3~7nm filter it will be much better, however I think that would require external guiding in order to get 5~10 minute subs...

I forgot to mention, I had the sbig @ -10c for the images.. used auto darks, no bias/flats used..

[Jen]

:thumbsup::thumbsup::thumbsup: nice pics Alex keep em coming :)

[Tilt]

That's a good start Alex, I gather your counter weights arrived?

Michael

[AlexN]

Michael : Hah... Nope, I had a 1kg g-clamp clamped to the front of the dovetail.. :) It worked, but wasnt perfect as it was heavier on one side than on the other, which when pointed up in the east, would pull the declination axis towards the north a bit... However I think I probably could have pushed the M16 subs out to 5 mins... I really want a narrower Ha filter to blot out the stars and stop blooming all together! :)

[jjjnettie]

Glad to see you've taken the new girl out Alex.
Hope to see you both at Ron's in a couple of weeks.

[Hagar]

:thumbsup:Looking good Alex. The scope looks like a keeper. Try to make it the longest owned scope you have.:lol::lol::lol::P:lol::lol::lo l:

[AlexN]

JJJ, I was happy to see it mounted up and imaging myself.. Its been far too long!

Doug : I think this one will last me! Got a few new bits and bobs i need for it, a motorised feathertouch is on the way which will make it that little bit nicer! Need an external guiding setup though... Guiding through Ha filters is flakey at best...

[Paul Haese]

I did not see any dewing up on the secondary on my first run. It was certainly a dewy night, might have to investigate making a dew shield myself.

Are you still using the same focusor? I had assumed you were. M16 is probably the best in this lot. Perhaps the sharpest of the lot. I found focusing this beast was a little hard and I will be getting a bahtinov mask made up for it.

Did you check collimation before hand?

[AlexN]

Paul: It still has the GSO focuser on it, and CCD inspector says there is tilt involved... I preformed an eyeball collimation on hadar before imaging.. It looked good, but CCD inspector tells me its about 3.7" off or there abouts.. So still plenty of room for improvement in this department... Curvature of 12.9%...

I agree, M16 is by far the best of the three images, but by no means a "Great" image.

Focusing was difficult but I got by after quite a bit of messing around...

[Alchemy]

interesting. i use a 2 inch eyepiece dewstrap with a thin lead and wrap it behind the collar on the secondary in my newt, glue the wire to one of the spider arms. ... it works for me.

[telecasterguru]

Alex,
Good to see you up and running with the RC.
Images look pretty good as well. Can't wait to see some longer exposures.
Frank

[AlexN]

Yeah that was what I was considering... Definitely want to find a way of sticking the wire to the spider that doesn't at all affect the diffraction spikes though... with a different imager (ie - higher resolution) they look quite grand out of these scopes.. Thats one of the drawbacks of the ST9, because the pixels are so large, a very long FL is required to get a high resolution shot.. I think in the RC the ST9 gives ~2.5 arcsec/pixel, whilst this is good enough given the standard of seeing I get, the diffraction spikes look a little unweildy in a longer exposures... I took a 3 second sub of Hadar after completing collimation and the diffraction spikes touched every edge of the image... Hadar itself was nearly 1/80th of the entire frame.. just the one star! I'm organising a bigger chip to get a bit more field of view and a bigger final image in the next few weeks.. Hopefully I'll get some nice shots from that too...

[TrevorW]

Nice one Alex still too warm here for dew to be an issue

Cheers

[Peter Ward]

Not sure I agree with your analysis Alex.

Did you apply the correct focal length and pixel image scale into CCDinspector? Using an FL of 1625mm and 2.52 arc sec per pixel and your uploaded M16 image I get FWHM's of around 6 arc sec and a 25" collimation error. (see attached)

The sampling at the FL you are using is fine. It's only when stars start to look blocky that you have an undersampling problem.

[AlexN]

Peter, Im using an old version of CCD Inspector.. Maybe thats the issue, or maybe I didnt apply the correct focal length and pixel scale in...

25" collimation error is pretty damn drastic.. and given that, Think the images are fantastic... Back to the old drawing board with collimation... Any hints on collimating an RC? I dare say you've had some experience with the task, however I'm reasonably sure the collimation on the RCOS 14.25" is electronic is it not? Do you do your collimation through CCDinspector or through an eyepiece? mine was eyeballed with a 10mm ep..

Cheers for letting me know I've got plenty of room for improvement... Definitely makes me wonder what this setup is capable of...

[TrevorW]

Peter

Under which part of CCD do you put these figures in and what pixel arc sec would I use for a Canon 350d DSLR

Thanks

[AlexN]

Yes, I ment to ask that too! Cheers for bringing that up Trevor.

[multiweb]

Pretty good start Alex. You've got a real nice rig there. Gets only better from there on. Keep at it. :thumbsup:

[Peter Ward]

Alex, Trev,

You can set these parameters in CCDinspector 2.0 under Settings> "default image properties"

That said, many CCD programs have an image or telescope setup menu item where you can enter the telescope FL and aperture, as well as observer name which are written to the .fits header.

These details are read automatically by CCDinspector. Default values (almost certainly incorrect) would need to be edited before CCDinspector would return sensible numbers.

Using a DSLR (or any colour camera) you may not be able to get a truly accurate number as the de-bayering routine may be non-linear.....
This would be an interesting topic in itself!

I've also done a CCDinspetor run on my RC using a ST9e field. (attached)

[Paul Haese]

Man I am happy with my collimation in that case. I managed 1.6" on my collimation. I was using live view and just went at collimation like I always do. Typically the seeing at Clayton is around 1" on most nights, so I need to attack it more. In your case, can you use live view on the ST? I found using that gets you pretty close. However the tilt being created by the focusor is not consistent either. Once you get that collimation correct you are gonna get images as sharp as the ones I got on my first night.

Thanks for the heads up Peter. Once again collimation is king for folded optics.

[AlexN]

Thanks for the info Peter... I like the look of what CCDinspector gives you for the 3d plot! :)

I'll definitely give collimation another go next time I get out...

[Peter Ward]

1" !!! ??

The CFHT telescope on Mona Kea typically only gets at best around 0.5"

Most sea-level sites are around 2-3 arc sec.....knew I shouldn't have left Essendon for Sydney :)

[Paul Haese]

Yeah it is pretty good there, pity it is a drive of an hour from here. I would like it to be a bit closer for planetary imaging. Have not seen a bad night there yet. Might be just an aberration I suppose but definitely the place to go. Should have gone there last night.:sadeyes:

Clayton SA btw, not in Melbourne Peter.;)

Lets get back on topic. Sorry Alex for the divergence.

[AlexN]

Paul : I can try to use short exposures with the system defocused a little to sort out collimation.. Will definitely give it a burl, because at 25" out, no wonder the data looks a little damp.. :D

Its funny because the diffraction rings were concentric and evenly spaced.. the scope gave razor sharp views through the ep.. stars resolving into tiny little spots of light right through the FOV... the only thing I did notice was a shadow around the edge of the field of view on one side of the EP.. But how could the diffraction pattern look collimated if the mirror was so poorly tilted as to cause a shadow like that? I dunno.. will have to look at it further..

Alex.

[Paul Haese]

So you cannot see it live and moving Alex?

If not maybe use your old guide camera. Mind you the flex is not the same from the weight.

CCD inspector should be able to use a generic software for capture that way you can see which way you have to go. I did find the live view very easy though.

[AlexN]

Nope Paul.. No live view as such.. there would be a few second delay between capturing a frame, downloading the image and seeing it... I dont have any other camera at the moment to use.. However I should have a QHY5 in the next couple of weeks to play with... that should help... Feathertouch still hasnt arrived yet :( sooner the better I say... As soon as that arrives, I can leave focusing this beast up to ccdsoft and focusMAX! :)

[TrevorW]

http://www.astro.shoregalaxy.com/dslr_calc.htm#details

this one will help calculate pixel arc second

[leinad]

Does the focuser have a baffle tube like the VC200L ?
It may be that that focuser collimation is out, causing a shadow when light casts in and against the baffle tube to the EP? Is there a site around that shows a detailed diagram of this RC ? I cant find any.

[AlexN]

Theres a primary baffle tube up the center of the tube like the VC200L, and the focusers collimation can be adjusted So I guess maybe that I should try to center the focuser to the tube then collimate the scope again... I just dont want to do anything too rash incase I cant get it back! :D

Ahh the joys of new toys.. I was scared to collimate the C11 when I first got it too.. it quickly found a spot on my "before every imaging session to-do" list. I suppose eventually this scope will be the same..

Paul - As a side note, with my ST9E I've only got the focuser racked out about 8.1mm, so the flex should be minimal.. I had the focuser positioned upside down as I read somewhere that that helps..

[TrevorW]

No diagram and I've emailed GSO but haven't had a response maybe someone could ask Lee A to contact and get for us

Cheers

[AlexN]

I did find it odd that the scope came with no collimation instructions (or any instruction manual what so ever).. You would think that with something as collimation touchy as an RC they would give you a run down on how to properly preform accurate collimation... Even a brief description of what to do if you see "insert description here" sort of deal..

I might call andrews tomorrow and see if we cant figure something out.. I need to get another vixen rail for the scope anyways.. may as well organise some sort of collimation instructions..

[leinad]

Interesting. I guess then temporarily you could check out the Vixen coll. guide and get a feel for similarities if they exist.

here: http://www.vixenamerica.com/pdf/scopes/VixenNorthAmerica_VC200L_Collimate. pdf

[TrevorW]

I was wondering what the hex bolts and grub screws right next to each on the back plate where the focuser attaches are for and looking at the Vixen collimation guide it would appear they are to collimate the focuser



Cheers

[AlexN]

Trevor, those are for focuser collimation... to be sure that the focuser is square with the mirrors... I'd assume getting it right would be a real pain in the BUM!

[TrevorW]

Sorry Alex you must have psoted when I found the answer to my own question

I'm not touching those until a) I've replaced the focuser b) everything else fails

Cheers

[AlexN]

leinad - Cheers mate.. that actually might be helpful to at least get me started.. They are fairly similar, excepting that the VC200L has an adjustable primary, where as the GSO RC primary is fixed...

Alex.

[Peter Ward]

OK this may take some effort.....Does the secondary have a central dot?
(usually applied with a permanent marker by kind manufacturers)

If no....then, make a thin cardboard mask with the same diameter as the secondary and put hole in the middle (cardboard..not the mirror :) ) , put it over the secondary and apply a dot via said hole.

Use a laser collimator to put laser spot over above dot on mirror.

Adjust the secondary to put the spot on the dot. You are almost done.

On a night where you can actually see an airy disk, have a look at a say mag 4 star.

Center it.

Do the diffraction rings look symmetrical?

No? then adjust the secondary to make it so. Remember *tiny* changes (eg Max 1/8th turn)

When the diffraction patterns are as round as you can make them, you are done.

Be happy or buy a better instrument! :)

[AlexN]

Cheers mate.. I just took a look through the scope with a cheshire eye piece and the secondary was off by quite a bit.. It doesn't have a center spot, that sure would be nice...

I'll look into the idea of centre spotting the secondary at a later date, for now, the cheshire made a big difference I now have all the rings looking down the scope concentric, they were quite a way out, somewhere in the vicinity of the 25" you mentioned.. :) I should have it out again this weekend, I'll point it at a star and see what I can do.. (provided the conditions are suitable...)

Cheers mate. I appreciate your input...

Ps. send me the cash and I'll buy an RCOS too :D

[TrevorW]

The Chesire helped, let me know for sure when you do a star test and I'll buy one

Analysis of an image using CCD returns varying results depending on whether you use monochrome, bayer matrix, what arc pixel size, camera pixel size, what saturation level etc etc

Cheers

Cheers

[tornado33]

Im glad I read this thread. I just installed CCD inspector and it returned this result with the 10 inch F5,6 scope. I had earlier collimated is using a standard laser collimator, first aligning secondary by putting laserspot onto centre spot on primary, then adjusting primary to get spot centred back at its source. Though the scope has a full thickness pyrex Sutching mirror, the tube is only thinnish gauge sheetmetal, and the cell is only a simple 3 point one, but the collimation still seems okay.

I used a 10 minute sub from my He2-72 image, taken with the modded 350D, as the test image. (baader MPCC coma corrector fitted)

FWHM around 3 arc secs, not bad for hand guiding on a mount with a plastic RA gear wheel :)

I am keen to try CCD inspector with my 6 inch F3.6 SN, it I suspect will be very finnicky due to fast focal ratio.

yes I thoroughly recommend centrespotting the primary mirror. Collimation errors with the secondary show up instantly with a laser collimator and the centrespot.

I also turn the laser collimator in the focusser, to make sure the laser is exactly parralell to the focuser axis. Mine wasnt and so i had to "collimate the collimator" till it was. When turning the collimator the laserspot should remain stationary.