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August STOG

PostPosted: Sat Aug 03, 2013 12:43 pm
by DaveMcC
Here is the August STOG target list:

As before the ‘standard’ star-hop unit of measurement is a 5 degree finder, North up. For reference I am using either the Cambridge Star Atlas (Map #18, 19) or Norton’s Star Atlas (Map # 13) and the draughtsman’s multi-hole stencil I described on the course, to plan my star hops.

Altair in Aquila (the Eagle) is the bottom star in the “Summer Triangle” mentioned on the course. It has a star each side sometimes called ‘the sentinels’. Will be due south at about midnight GMT on 8th August.

1. Altair – has an optical 9.5 magnitude double
2. Beta (Alshain) is the southern star of the two ‘sentinels’. It has a faint red dwarf companion at magnitude 11.6
3. Eta – is a Cephid variable with a period of about 7 days, range 3.5 to 4.4. It is 5 degrees south (down) from Altair so put Altair in the 12 o’clock position of the finder and it should be at 6 o’clock in finder (assuming we are looking at or about midnight GMT on 8th )
4. NGC6709 – is a loose open cluster. Go back to Altair. Put on edge of finder at 6 o’clock (North ‘up’) then move to West about one finder until a small group of three stars in a triangle, the brightest is zeta. Diagonally down and to the West is NGC6709. It has two almost straight chains of stars and two brighter stars close together giving impression of two eyes.
5. Gamma Delphinus is double with yellowish primary magnitude 4.4 and greenish companion magnitude 5.5. From Altair in the 6 o’clock position of the finder, move left (East) about two ‘hops’ don’t move ‘scope up or down. The whole of Delphinus should just about fit in your finder. Remember it’s a sort of kite shape, with a tail to south south west. Gamma is the topmost star of the ‘kite’ part.
6. Struve 2725 in same main scope field as (5) to SW but fainter at 7.7 and 8.5

Re: August STOG

PostPosted: Thu Aug 08, 2013 10:19 pm
by DaveMcC
Tuesday 6th August 23:30 BST.
Clear sky, but a bit milky from the pub light pollution.

Using 200 mm f10 SCT, Fork mounted RA with drive. Manual setting circles as required to nearest degree in declination, and set up RA on Altair in Aquila, and fitted the Telrad finder. Prism Star Diagonal fitted, North is up.

23:00 BST
Altair (#1) - can’t see companion star
Beta (#2) - can’t see companion star

23:30 BST
NGC6709 (#4) 18mm ED e.p. (x113) 18h51 +10. I resorted to using setting circles to locate it. This open cluster looks nothing like the description given. Had to compare to “The Night Sky Observers Guide Vol 2” fig 32-1 to see photo to compare with. Two meteors passed the f.o.v N to S while observing this.

00:01 BST
Eta Aquila (#3) 40 mm (x50) 19h52 +1. Cant see ant stars in f.o.v. to compare with. Swap to 7x35 bins. Dimmer than delta (3.36) brighter than iota (4.36) so my estimate eta at magnitude 4 tonight.

00:15 BST
Gamma Delphinus (#5) 18mm ED e.p. (x113) 20h46 +16. Once located swap to illuminated reticule 12mm e.p. Sep 1 small division translates to 10”, estimated PA 270 degrees. Book values are 9.6” and 267 degrees – quite pleased with my measurement.

00:30 BST
Struve 2725 (#6) 9.5mm ED e.p. (x214) 20h46 +16. Same f.o.v. as #5. Found initially in 18mm but not resolved as a double until switching to the higher power. Once located/ confirmed swap to illuminated reticule 12mm e.p. (x163) too dim to use a barlow lens to get a better measurement estimated at ½ small division or about 5” and PA either 350 or 10 degrees. . Book values are 6” and 11 degrees – so again quite pleased with my measurement.