Wednesday, June 17, 2020

better data on NGC 6520 (Bradford)

12:08. I thought about workflow. If I had more time... Often when imaging, I would aim at a target, still with an eyepiece in the 'scope, centre on it, then mount the camera. Then you'd know you're on target. [ed: Another approach at field identification is plate-solving.]
Instrument: Celestron 8-inch SCT
Mount: Vixen Super Polaris
Method: slewing and tracking with IDEA GoToStar
I just didn't think that would work given the V-notch in the trees... I had to front-load focusing (with a Bahtinov), using a bright star. OK. I modified the workflow:
  1. mount the camera
  2. focus on a bright star
  3. slew to the area near the target
  4. double-check focus
  5. sync
  6. slew to a visible object even closer to the target and sync, if nec.
  7. slew to the target
  8. identify/verify the field
  9. shift, if nec.
Hopefully, I'd be pointed right at the object. Steps 1 through 6 could all be done well in advance. Then I'd wait for NGC 6520 to come into the clear patch.

Checked the conditions: 46%, 15.1°, pressure falling, rain tomorrow, no extreme weather alert!

Camera rigged up and powered. Ditched the LED keyboard light for the camera control cable. EOS Utility launched. Got the loaner Kendrick Bahtinov mask ready. Started BYE. Considered Rasalhague. Looked for an object in the observing list in Oph. Did sync then slewed. Hoping it would work as I was a little blind with the camera in. Really close but still had to pan using the finder. Frame and focus mode. Fine-tuned the position. Installed the mask. Focused carefully. Removed the mask.

12:20. Wondered why I was not seeing any of the stars I needed. Did a sync.

Looked for a nearby star. Slew to cursor. Dropped the wall again! Panned to the target star. Checked the camera settings from yesterday. 25 seconds at ISO 3200. Did a test shot. Frustrated. Got it! I verified I was on HR 6766 in Sgr. Camera was oriented roughly north up, east left. Synced. Slewed. Took a shot...

12:36. Checked it... Some good markers... Right there! NGC 6520. Right in the fire truckin' centre! On the hand controller, I pressed the right hand movement button for 3 seconds. A bit better, that moved the open cluster a bit left in the frame. Programmed the gap time. Entered the filename info. And started shooting!

Saw a flash in the sky near Serpens... The left Serpens. [ed: Cauda!] Why can't I remember which one is which?

12:47. Really darkened, due to the tree.

12:50. Cleared the tree! Woo hoo! It was working. What a great thing, sorting out the sync. So I had good focus, better pointing, still questionable polar alignment. But overall, I was very happy. Last night, that was great, symbolic. Tonight, icing on the cake.

It went well. Good conditions... clear.

The mount was drifting up and right, i.e. west.

The batch completed. I triggered another round.

Took in the whole sky enjoying various constellations. Noted Ophiuchus, Serpens, Aquila, Sagitta, Corona Borealis, Cygnus, Vulpecula, Delphinus, Draco.

Good images...

[ed: 1:01. Power died in the recorder.]

1:06. Started fading as it moved into the next tree. Sweet. A good 15 minute capture! Good data to stack. Some good frames.

Couldn't think of any particular object to photograph. Unmounted the camera.

1:10. Started the darks run, camera on the ground.

Considered flats but I didn't want to leave the camera installed.

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