47 Tucanae NGC104

[TrevorW]

47 Tucanae or 47 Tuc is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.01 kpc away from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches.
Distance to Earth: 13,050 light years
Apparent magnitude (V): 4.09
Right ascension: 00h 24m 05.67s
Declination: −72° 04′ 52.6″
Radius: 60 ly
Constellation: Tucana
Distance: 4.45 ± 0.01 kpc (14,500 ± 32.6 ly)

90 minutes in 3min subs captured 30/8/23 under a full moon Bortle 6 between 8 and 10 before the wind picked up https://static.xx.fbcdn.net/images/e...1/16/1f642.png

[Dave882 (David)]

One of our most stunning globs for sure! Great star colours Trevor although I think the wind (or focus shift?) may have affected the sharpness of your stars a bit during the run.

[TrevorW]

Yes could have been a bit of both

[gregbradley]

Good going on trying this difficult to tame bright core glob but your focus is off.

Greg.

[TrevorW]

I've checked the collimation on the GSO 10" Truss RC and used a mask and everything seems in focus so I'm not sure what caused this. Captured with an Optolong L Pro filter. I'm wondering if the optics are an issue or is the filter causing this.

[Startrek (Martin)]

Originally Posted by TrevorW

I've checked the collimation on the GSO 10" Truss RC and used a mask and everything seems in focus so I'm not sure what caused this. Captured with an Optolong L Pro filter. I'm wondering if the optics are an issue or is the filter causing this.

Trevor,
Focus can shift even over an hour due to many factors like focuser tube mechanical movement and atmospheric conditions ( humidity, temperature etc.. ) I don’t use auto compensated focuser software , just an ZWOEAF on manual control but I do check my subs “on the fly” during an imaging session to see if focus is stable. It may save an imaging session having a periodic look ( every 20mins or so )
Also filters can change your backfocus by up to 1mm ( divide the thickness of your filter glass by a factor of 3 )

Cheers
Martin

[gregbradley]

Temperature shifts plus cool-off time causes focus shift.

For example my AP Honders typically shifts focus after the initial hour and then tends to be stable with minor shifts with lower temps.

A Tak FSQ shifts focus quite a bit with every 1 degree C drop.

Greg.

[TrevorW]

Ok so best check focus during image run then

[petershah (Peter Shah)]

lovely star colour but does look slightly soft...periodic focus will help