Imaging with the 130pds

[JimFR]

Here's my m45, m42 and m31 with 130 PDS..

All 3 min unguided subs with canon 1100d

M45

http://www.astrobin.com/140413/

M42

http://www.astrobin.com/124109/

M31

http://www.astrobin.com/122877/

Thanks,

Ishan.

Excellent! How precise are your exposure lengths? Do you time manually or tether to a laptop?

I have tended to limit myself to uding the M mode on my Pentax, not been brave enough to try B yet [emoji15]

[Ishan Mair]

Excellent! How precise are your exposure lengths? Do you time manually or tether to a laptop?

[emoji15]

I use a laptop..helps a lot with polar alignment and field selection..not to mention autoguiding when I get the Orion MMAG.

[Uranium235]

Just a little WIP to keep it simmering nicely.... caught this a couple of nights ago under probably the best sky of the year. However - the gear got rained on (slightly!), so there was a nervous check on the primary mirror - glad to say it was just one small spot.

Hoping to finish it off Friday night.

 

[Uranium235]

A quick run out for the 130 at f4.5 last night, it hoovered this lot up in just 2.5 hours - easy to see where this one is going

[happy-kat]

I really enjoy the images shared from this telescope. The detail and stars just seem so deep and velvety.

[Clockwork_Orange]

Stunning is the only word that come to mind Uranium, cant wait to see the end result.

Regards

JP

[Uranium235]

Clockwork_Orange, on 30 Dec 2014 - 8:16 PM, said:Clockwork_Orange, on 30 Dec 2014 - 8:16 PM, said:

Stunning is the only word that come to mind Uranium, cant wait to see the end result.

Regards

JP

Cheers

Heh, neither can I!!! Ive been hankering after an mosaic of this area ever since I started AP - and now that tree is going down next door, I can get a full night on it rather than having to wait until it crosses the meridian.

[DaveS]

I'm seeing enough from this little jewel to give me a hankering, especially at the price, something I could buy on spec, so to speak.

So what are the gotchas?

OK, it needs collimating, but how bad is it? I remember collimating my old 8" newt,which was a pain and it was f/8 to boot, not f/5. Am I really going to have to collimate before every session? If yes, and it's going to take an hour or so then forget it, there isn't that much imaging time to waste, especially during the week when I turn in at 10.30.

Star spikes I'm aware of, just have to decide how much I dislike them, and If I can live with them.

How bad is the focuser? I know it's a crayford and thus suspect as it doesn't have the robustness of a R&P. The crayford on my Meg 90 is a disaster as it cannot pull the camera in on its own. I have to give it a push. If the Skywatcher is anything like that then I'd have to replace it, and a Feathertouch is 21/2 time the price of the bare OTA  .

I'll need a coma corrector obviously, and I think I'd go for the Baader given the comments I've seen re: the Skywatcher one.

So it could go from cheap 'n' cheerful to quite serious very quickly, and I just want to know what I'd be letting myself in for.

[JimFR]

The focuser is pretty sturdy - it is quite happy with my fairly ancient Pentax ist DS - even when mounted via a 2x T-thread barlow in the 1.25" to 2" adaptor.

Collimation should be a 5 minute job. Not done it a lot on this TBH, but it is fairly tight and doesnt alter much...that being said I'm not that picky, and the seeing is pretty pants here anyway!

Hope this helps!

[Uranium235]

DaveS, on 30 Dec 2014 - 11:04 PM, said:DaveS, on 30 Dec 2014 - 11:04 PM, said:DaveS, on 30 Dec 2014 - 11:04 PM, said:DaveS, on 30 Dec 2014 - 11:04 PM, said:

I'm seeing enough from this little jewel to give me a hankering, especially at the price, something I could buy on spec, so to speak.

So what are the gotchas?

OK, it needs collimating, but how bad is it? I remember collimating my old 8" newt,which was a pain and it was f/8 to boot, not f/5. Am I really going to have to collimate before every session? If yes, and it's going to take an hour or so then forget it, there isn't that much imaging time to waste, especially during the week when I turn in at 10.30.

Star spikes I'm aware of, just have to decide how much I dislike them, and If I can live with them.

How bad is the focuser? I know it's a crayford and thus suspect as it doesn't have the robustness of a R&P. The crayford on my Meg 90 is a disaster as it cannot pull the camera in on its own. I have to give it a push. If the Skywatcher is anything like that then I'd have to replace it, and a Feathertouch is 21/2 time the price of the bare OTA  .

I'll need a coma corrector obviously, and I think I'd go for the Baader given the comments I've seen re: the Skywatcher one.

So it could go from cheap 'n' cheerful to quite serious very quickly, and I just want to know what I'd be letting myself in for.

Ok, the 130.... its not as difficult as you might think.

Firstly, collimation. No, you will not need to collimate it every time - in fact, months can elapse between collimation - and even then its only out by a small amount. Mine normally gets done when I take the imaging train apart for cleaning. But getting it right first time does matter, you need as little tilt in the secondary as poss (preferably none), that will ensure your field is corrected properly by the coma corrector.

Secondly, focuser. It helps to know the combined weight of your imaging train (camera, FW, corrector), anything up to 1kg is fine - but you may need to tweak the tension grub screws a little to get it "just so" (this is normal on any scope ive owned). You will also need to drill and tap a third thumbscrew hole in the 2" EP holder, that improves the rigidity considerably. Unfortunately, there is no replacement focuser for this telescope so you have to work with what you are given (makes it more fun!!).

My imaging train is ~1.6kg, the 383, 2" FW, tilt adaptor and corrector make for a fair old lump - but it copes alright. However, to cope with the weight (and cos I hate push-fit) I did have to convert my focuser to a threaded connection (custom built adaptor).

Third, corrected field. Your CCD chip is smaller than the 8300 right? Then either the Baader or SW corrector will suffice (both have pros and cons), your corners should be pretty good with that sized chip.

Fourth, performance. Again your CCD has small pixels? Going 2x2 bin at that FL with those sized pixels you could pretty much tear strips out of the sky with it and still get a good image. F5 (or F4.5 with the SWCC) @ 2x2 totally wipes the floor with f6 1x1 (in terms of signal to noise). Going from a frac to a newt may be a bit of a shock and you may think it looks a little "softer" or less contrast than a frac - but what you have is speed and depth of signal..... and if you have lots of signal then sharpness and constrast can be won back at the processing stage.

Other stuff:

1) Bottom end, make a cover for it or you will get light leaks

2) Flats, can be a pain in the rear end at times. So once you have a good set, dont touch the camera!!!

3) Sweet spot: If you have a slightly dodgy corner, slew to a bright star then place it toward the affected corner (about 2/3 way out) - refocus (using the B-mask), then that should balance the field out. But its unlikely you may need to do that given your chip size.

Hope that helps

Oh, forgot to add... the 5" primary isnt what you would call heavy, so there is a good chance you will be camera heavy. I strapped x2 0.5kg leg weights to the bottom of mine so it balances out without me having to slide it all the way back in the mount saddle.

[DaveS]

Many thanks for your replies guys. Lots to think about, but pushing me towards the "buy" button as I've seen nothing that could be a deal breaker for me.

I'll weigh my imaging train, but it shouldn't be too heavy.

As a note, I've been running my rig with the WO 0.8 F/R IV and binning 1x1.

[Uranium235]

It will be slightly faster than the WO, but with more focal length. And with your cameras pixel size, the resolution will be 1.44" p/p (2.88 binned) - anything below 3.5" p/p is useable, its down to personal preference really. It would help if you knew your camera's gain between 1x1 and 2x2, mine was measured at x2.23 (however I suspect the Sony chip will be a little lower). Easy way to do that is take some flats at 2x2 and achieve a target ADU (something like 24000), then switch to 1x1 and then see how long it takes to achieve the same ADU level - divide one by the other, and there you go! Another way is to do it under starlight using a non saturated star.

If im working on just 1-2 panes I usually go 1x1, but for more than that I opt to take a hit on the resolution but halve the time it takes for each pane - so its pretty easy to rack up a large scale image quickly. I'd like to figure out a way to combine both types of data in a sort of "halfway house" of signal and resolution.

[DaveS]

Well, I've been to FLO and ordered a 130 PDS, a MPCC and two Bahtinov masks (For the 130 and Meg 90). I already have a Premium Cheshire collimator, so fingers crossed!

[sidelight]

Well its been a long time since I had a chance to get out and the weather has obliged but I did get one night over the Christmas break 

and 

Cheers

Ross

[Uranium235]

DaveS, on 31 Dec 2014 - 2:01 PM, said:

Well, I've been to FLO and ordered a 130 PDS, a MPCC and two Bahtinov masks (For the 130 and Meg 90). I already have a Premium Cheshire collimator, so fingers crossed!

Welcome to the club!

Good news is that you have the MPCC, which maintains the parfocal nature of the 130. So no need to refocus between Ha and OIII (done it for myself).

It will require more cooldown time than your frac, about 30min until its settled down enough to get good feedback from the b-mask. If you do it hot, the pattern jumps about all over the place making it difficult to judge.

Two things you need, the spacing for the MPCC:

From bottom of T2 thread: 55 (quoted), 57 (actual)

From bottom of M48 thread: 57.5 (quoted), 59.5 (actual)

The numbers marked as actual are what I needed to do in order for it to cover the 8300 chip.

[DaveS]

Thanks Rob, those figures are just what I need. I went for the MPCC after reading most of this long thread with people saying the MPCC was parfocal but the Skywatcher wasn't

[laser_jock99]

If you get a Baader MPCC make sure it has been machined correctly. I had to send one back after I (eventually) realised it wasn't sitting orthoganally in the 2" holder when clamped up due to poor machining.......

[DaveS]

OK, I'll be sure to check that out. Would have expected better from Baader though TBH

[DaveS]

Mr Fed-Ex has just been and delivered my new baby

[Russe]

Just had my baby out after almost a year with the new camera - and suddenly it started raining. So I hurriedly ran everything inside. Now, 30min later it's clear skies...

I'm going to sleep...

[DaveS]

Oh, dear!

It's still clear here but I'm imaging with my Meg 90 ATM, first light will have to wait until later in the week after I've had a chance to collimate it. I've been reading up on the procedure but can't find any good tutorials. Did find some videos but the guy waffled so much I gave up.

[frugal]

Just had my baby out after almost a year with the new camera - and suddenly it started raining. So I hurriedly ran everything inside. Now, 30min later it's clear skies...

I'm going to sleep...

It has been on-again, off-again all evening east of the river as well.

[Thalestris24]

Hi all

Anyone know if you can attach a Skywatcher autofocuser motor (or other autofocuser) to the 130pds?

Thanks

Louise

Edited January 14, 2015 by Thalestris24

[tingting44]

Hi all

Anyone know if you can attach a Skywatcher autofocuser motor (or other autofocuser) to the 130pds?

Thanks

Louise

Yes you can attach SW auto focuser, no modification needed

Edited January 14, 2015 by tingting44

[DaveS]

Oh, dear!

It's still clear here but I'm imaging with my Meg 90 ATM, first light will have to wait until later in the week after I've had a chance to collimate it. I've been reading up on the procedure but can't find any good tutorials. Did find some videos but the guy waffled so much I gave up.

I found Astro-Baby's tutorial, very clear so I've bookmarked it. It's been decades since I had to collimate a newt (My home-built 8" f/8), the turorials refreshed my memory, so I'll be giving it a proper go.

But imaging will have to wait until I get the USB socket of my SX filter wheel repaired.