NGC1055 and its adjacent galaxies

[tim.anderson]

Compiled from seventy 180-second exposures using a Skywatcher Esprit 100mm refractor and an ASI2600MCProDuo mounted on a ZWO AM5 mount

[tim.anderson]

And a close-up of NGC1055

[OzEclipse]

Hi Tim,

Very nice image.

There are two dark marks on the image, one midway between NGC 1055 and M77 and the other just off the midpoint between NGC 1055 and NGC 1032 from frost/stains on the sensor window or are they something inherent in the sensor? How difficult is is to clean the sensor window without leaving more marks? What do you use?

cheers

Joe

[tim.anderson]

I think they are dust motes on the inside surface of the objective cell. V difficult to remove without disassembly of the scope. I clean all the other surfaces with isopropyl alcohol and a soft lint-free cloth

Tim

Tim

[OzEclipse]

Hi Tim,
Definitely not dust motes on the objective. Anything on the objective will be completely out of focus. It's something closer to the sensor.
Joe

[tim.anderson]

Joe

Fortunately, I can test it:

1. rotate the camera alone - if the marks move, therefore the marks are on the sensor cover
2. rotate the field flattener alone - if the marks move, therefore the marks are on one or other surface of the flattener
3. If the marks have not moved in scenario 1 or 2, therefore the marks are on one of the surfaces of the objective cell

I have cleaned the sensor cover, the outward faces of the flattener unit. and the outside of the objective cell thoroughly but the marks remain.

Of course there are three other possibilities:

a. that dust has infiltrated inside the camera sensor cell
b. that dust has infiltrated inside the flattener unit and is sitting on one of the inner surfaces
c. that dust has infiltrated inside the triplet objective cell and is sitting on one of the internal surfaces

I doubt that I have the skill to ameliorate a, b or c, and may need professional attention to the scope. In the meantime, a good set of flats is called for.

Tim