Lodestar X2C third session

[arkosg]

Hello all,

Between the fall rains we had a clear night, so I got out with my CPC 800 HD 8" alt/az Celestron & f/3.3 focal reducer, 

using the Lodestar X2C with Lodestar Live v 0.10 on a MacBook Pro.  A waxing crescent moon had already set, and 

skies were clear,  but humidity was high and seeing was not as steady as I'd hoped it would be.

I was able to use darks for the first time, bypassing the "save & restore" option and just shooting darks and using them.  

I did notice that as the evening went on (a few hours later), not all the hot pixels were being removed, though overall the 

images were well corrected for hot pixels and the stacking modes worked better than on previous runs.  Temperatures 

did drop appreciably from the start of my session (and when I took my darks), but I couldn't muster the enthusiasm to 

remove the dew cap, cap the scope, and shoot new darks.  Do others find they are redoing or adding to their darks?

Focus is proving to be tricky as well.  I have replaced the standard SCT focus knob with a Feathertouch Micro 10:1 focuser 

which helps, and use LL's focus assist, but I find the focus still drifts (even with the mirror locks) and I have to refocus as 

best I can on the fly.  It is frustrating, especially the "back and forth" to try to get close to true focus, and I am considering 

some sort of electronic motorized focuser.  Anyway had any experiences with JMI or Starizona's kit in this regard?  Helpful?

I also had trouble with colour correction, especially with dimmer objects.  Often, even with "standard operating procedure", 

I find the histograms too small/narrow to easily match them up fully, and find I have to try to fix this after the fact in iPhoto.  

I'm looking forward to LL 0.11 and seeing if that makes it easier to get consistent colour correction on my images!

I have placed an assortment of shots from this third session into my gallery; here are a few highlights.  Enjoy!

- Greg A

 

 

 

 

[HiloDon]

Great shots, Greg! And, nice selection of objects. I have found the same thing with respect to darks, even with the mono. I just drape a black bag over the dew shield to get the darks. You could use a plastic garbage bag. I have the JMI focuser for my Meade 8" SCT and it works great. My mount sits outside my observatory room and I have an extension to the controller, so I can sit and watch the screen as I focus. It has two speeds which eliminates the need for a micro focuser. The Meade seems to hold the focus well and has very little shift when I do have to focus.

One other thing on darks. I usually take them at 15 seconds and then stack images to get the correct exposure. Then I don't have to save different exposure darks. It's also a very quick effort to update if noise starts creeping in. I really like Paul's sum stacking feature in LL.

Just a suggestion, but it would be nice to know what your exposure times are and if they're stacked. I think Paul is putting in some auto feature for stacking info in v0.11, but right now it has to be user entered.

Don

[laser_jock99]

Good set.

[arkosg]

Thanks everyone!  There is a learning curve, but it's neat to be able to get decent results even early on.

Don - good suggestion, re: garbage bag.  I'll remember to keep one about!  Do you find hot pixels, etc. 

start to "creep" back in after some time?  I was out for a while, and only took my darks at the start, so 

as the temperatures drop and condition change, I would think it makes sense.  Just wonder if others are 

also experiencing it, and if they are finding that shooting a few more darks solve the problem.  As you'd 

suggested earlier, I used 15 s darks matched to stacks of 15 s exposures.

Looking back I realized I had added exposure info in the gallery, but not here!  Oops... all of the above 

are 15s exposure, a mix of sum and mean stacking, with stacks ranging from 3 - 10 depending on the 

target (mostly around 5).  My mount does okay, but has some "jitter" (I'm looking into some counter 

weights to balance it better) and so that seems to work best for me at the moment.  I did notice this 

time out that sum stacking resulted in slightly noisier final images than mean stacking, all things being 

equal.

Is your JMI unit wired?  I'm not sure why it seems my focus was drifting as much as it was; perhaps 

the duration of the session & the dropping temperature had a role.  Certainly there was a lot of unsteadiness 

in the atmosphere which made even finding focus a challenge!

Cheers,

- Greg A

[HiloDon]

Thanks everyone!  There is a learning curve, but it's neat to be able to get decent results even early on.

Don - good suggestion, re: garbage bag.  I'll remember to keep one about!  Do you find hot pixels, etc. 

start to "creep" back in after some time?  I was out for a while, and only took my darks at the start, so 

as the temperatures drop and condition change, I would think it makes sense.  Just wonder if others are 

also experiencing it, and if they are finding that shooting a few more darks solve the problem.  As you'd 

suggested earlier, I used 15 s darks matched to stacks of 15 s exposures.

Looking back I realized I had added exposure info in the gallery, but not here!  Oops... all of the above 

are 15s exposure, a mix of sum and mean stacking, with stacks ranging from 3 - 10 depending on the 

target (mostly around 5).  My mount does okay, but has some "jitter" (I'm looking into some counter 

weights to balance it better) and so that seems to work best for me at the moment.  I did notice this 

time out that sum stacking resulted in slightly noisier final images than mean stacking, all things being 

equal.

Is your JMI unit wired?  I'm not sure why it seems my focus was drifting as much as it was; perhaps 

the duration of the session & the dropping temperature had a role.  Certainly there was a lot of unsteadiness 

in the atmosphere which made even finding focus a challenge!

Cheers,

- Greg A

Hi Greg,

I notice the noise "creep" in mono more than the color. Once I get the hot pixels out in the color LS, they don't seem to come back. You would think as it got cooler there would be less noise and fewer hot pixels. I'll check out your gallery for the exposure times and additional objects you got.

The JMI is wired to a hand controller. I just ran an extension through my conduit so I can focus at my terminal. Wish there was someway to remotely block the scope so I could take darks without going outside. I'm very close to a totally remote controlled system now. Not that it's cold outside here. I'm just lazy.

Don

[RobertI]

Hi Greg, I sympathise with your focus issues at F3.3. I have a similar problem with my C8 at F3.3 due to mirror flop and I had to readjust focus every time I moved to another object. HiLoDon and Nytecam suggested always finishing focus by turning counterclockwise as this moves the mirror uphil. I never got around to trying this before I got another scope with a fixed mirror and Crayfor Focusser which I am currently using. However I want to go back to the C8 at some point and if I cannot resolve focus issue I will probably try a Bhatinov mask to focus on nearby star before final slew to object. Like you , I find the focus assist feature of LL is accurate but somehow a pain to use with the coarse focus knob of the C8.

Rob

[arkosg]

Hi Rob,

I was particularly surprised by the changes in focus this past observing session - previously, I wasn't seeing 

the size or frequency of changes in focus that I noted this time 'round.  Not sure why it seemed so obvious 

this time, but there it is.  

In general, I find the focus on the SCT a bit finicky, even with the dual speed focuser upgrade.  I may need to 

check the collimation of the scope as well - it's been moved around a lot as of late, and I'm wondering if it's 

been bumped a few about in the process.  I saw the note about focusing CCW, which I have been doing, 

and it seemed like perhaps it was helping - until the other night.  I just don't want to spend so much time 

fussing with focus, especially since it's getting colder, and I'm outside with the scope using it!

Cheers,

- Greg A

[HiloDon]

Hi Greg,

I was thinking about your focus problem and did some research on it.  You have mirror locks, so it doesn't seem like mirror flop or movement is your problem.  You said you had an appreciable drop in temperature.  I found this interesting article that might explain what you experienced.  I took a close look at your images and your focus is excellent.  I don't think that collimation is a problem expect that you do have a bit of coma in some of the corners which could probably be eliminated with a precise collimation.  The f3.3 FR is very sensitive to collimation.

http://www.astropix.com/wp/2011/06/20/focus-change-due-to-temperature-variation/

Hope this helps.  

Don

[Martin Meredith]

Great captures there Greg! 

I can sympathise with the pain of focusing. My StellarVue is single speed and stiff, and moving to the Quattro dual-speed has been a real improvement. I have the Skywatcher motorised focuser kit to fit which I'll use to make mid-session tweaks, although I haven't noticed a lot of drift with the Quattro as yet. 

I sometimes replenish my darks during the session but not often. To be honest, I get carried away looking at the images and even when I spot some particularly bright pixel I don't care (until the following day, when it bothers me…). The plastic bag trick is a nice idea, Don. 

Since it is always interesting to compare different scopes, here's my own Fleas shot taken on Friday for comparison (8 x 30s mean stack). Very similar, I think, and some consistency in colour too! The core is a little burnt out.

cheers

Martin

[Paul81]

A great set of shots Greg, looks like you had a good session!

I tend to top my darks up through the evening, perhaps add 3-4 every 45-60 mins or so. Even though the ambient temperature drops, the cameras electronics heat the camera up over the course of a session, so there will be some fluctuation as the session progresses.

Paul

[arkosg]

Don - thanks for the article.  Very interesting indeed - especially as the cool season is upon us!   I was doing mainly visual work before the spring of this year, and there you are constantly adjusting focus anyway, so perhaps the effect isn't so obvious.  But setting focus for the camera.... where you "set it and forget it"... well, it definitely shows up (at least for me in this case)  Thanks for passing that article along.

Martin - I took your image and compared it to a rotated and flipped version of mine.  Kinda neat to see them side by side like that - interesting to see the effect of longer exposure & different hardware (not to mention viewing conditions!)  You have nice round stars throughout your image - what sort of mount are you using? 

Paul - thanks for the darks info.  Together with Don's garbage bag suggestion, I think I've got a procedure in place for next time! ;-)  Completely unrelated, but I've put in a LL "feature request" for you as you map out future versions of LL - please see http://stargazerslounge.com/topic/225754-lodestar-x2c-2nd-light-darks-issues/?p=2437157Thank you in advance for your consideration - and for a fun bit of software!

Cheers,

- Greg A

[Martin Meredith]

Martin - I took your image and compared it to a rotated and flipped version of mine.  Kinda neat to see them side by side like that - interesting to see the effect of longer exposure & different hardware (not to mention viewing conditions!)  You have nice round stars throughout your image - what sort of mount are you using? 

I'm using a Skywatcher AZ-EQ6 in alt-az mode, but the round-ness I think has more to do with collimation (in my case). I put quite a bit of effort into getting things looking good at the start of the session using an auto-collimator (mainly tweaking the primary, so quite fast). 

Martin