Spiral Galaxy NGC 4321 M100

I'm glad you all liked the image.

Dave,

The red areas are star forming regions.

The I band is photometric filter requiring a long exposure, because the QE of the sensor is 40% at 950nm. The H Alpha is a narrow filter again requiring a long exposure.

The Blue is a photometric filter already in the visible and quite broad as a visible filter, it only needs a short exposure.

The reason for the clarity and lack of overexposure at the core is the balance and guestimating of exposures. When multiple ones are superimposed the SNR and resolution improves.

I have avoided long exposures ie. 5 minutes, as I have discovered from experience that the central area washes out any detail.

Keith,

You're right, there is a lot of H Alpha showing up, and quite possibly as you say alot of star forming regions than our galaxy. I wonder if this makes it an older galaxy?

Eamonn A
MPC J62
www.kingslandobservatory.com

Eamonn,

These are incredible images you are producting with the 0.9m giant and especially in consideration of the short subs and total exposure time. I am very curious what kind of result you would get with slightly longer subs as well as slightly longer total exposure time? For example, with three hours of total data, I would expect to see some very serious results (not to suggest that there is any problem with the current results). You express concern about blowing out the core but this is something I would personally not worry about provided you do not exceed 65,536 ADU for any pixel. There exist non-linear stretching methods which can really bring up the dim portions of any image without adversely impacting the non-overexposed core.

Also, excuse me for asking but how much did the beast cost and what kind of wait time was there? With 0.9m of aperure, you have some serious photon collection ability.

Anthony,

Progressing to longer subs and longer exposure times should result in the outer arms being more pronounced. The gaseous areas in the outer regions should manifest into structure that wasn't discernable in the original image.

I take your point about non linear stretching to compensate for over exposure. In fact I actually did try this with a previous image which worked.

I actually hadn't planned such long exposures that you indicated. The plan was to image a number of galaxies and nebulae in a short time because of the opportunity of a clear sky.

I designed and built the telescope at my workshop here at Kingsland. It was designed in 2000. It was built by 2002. It was robotized and upgraded by 2006. It would be hard to put a value on it. The telescope would be on the same level as a professional research grade one.

Eamonn A

MPC J62
www.kingslandobservatory.com

I designed and built the telescope at my workshop here at Kingsland. It was designed in 2000. It was built by 2002. It was robotized and upgraded by 2006. It would be hard to put a value on it. The telescope would be on the same level as a professional research grade one.

Even more impressive in light of the above!

Just curious ...

(1) have you tested the optics with respect to PV and RMS?

(2) how suitable is it for a german equatorial mount?

With a 0.9m aperture, you can do some seriously wild work!!! :shock:

Anthony,

I have tested the optics with the following results:

1. Primary: Surface Accuracy: lambda/8 Peak to Valley @ 633 nm.
2. Secondary: Flatness: lambda/15 Peak to Valley @ 633 nm


The OTA was designed for a fork. However, it could be adapted for a GEM.

Eamonn A
MPC J62
www.kingslandobservatory.com

Wow .9m, that's some animal. What do you feed it .