More OIII

July 30th, 2008

The following image of NGC 6888 combines the previous Ha image with new OIII data. The OIII data is has definite focus issues, and I think the previous image is better from an aesthetic point of view, but this does show more the OIII portion of the nebula.

The Crescent Nebula (NGC 6888) – Ha/OIII Version 3
The Crescent Nebula (NGC 6888) – Ha/OIII Version 3

Imaging Equipment: WO ZS 80 II ED, DSI Pro II, Razorback Cooler, Baader 7nm Ha filter, Baader 8.5nm OIII filter, WO 0.8x Flattener II
Guilding: Orion 80mm ST, DSI Pro
Mount: CGE

Exposure: Ha (71 10-minutes subs), OIII (67 10-minute subs)

If you would like to see a spectacular image of this nebula, take a look at this image by Ken Crawford.

A Little Bit of Color

July 27th, 2008

Last night’s imaging session was once again NGC 6888, but this time with an OIII filter. Unfortunately the sky became hazy quite early, so the OIII images are very noisy. However, here is what you get when you combine them with the previous Ha images (Ha/synthetic/OIII).

The Crescent Nebula (NGC 6888) - Ha/OIII Version 1
The Crescent Nebula (NGC 6888) – Ha/OIII Version 1

Imaging Equipment: WO ZS 80 II ED, DSI Pro II, Razorback Cooler, Baader 7nm Ha filter, Baader 8.5nm OIII filter, WO 0.8x Flattener II
Guilding: Orion 80mm ST, DSI Pro
Mount: CGE

One of the problems that I keep running into is that the camera never goes back on the telescope in exactly the same plane as it was before. This causes problems when stacking images, with some sections of the image perfectly aligned and others off by several pixels. This can be fixed to a certain extent with post processing tools, but I would really like to figure out a way to attach and reattach the camera without having the focal plane tilt.

A Little Bit Longer

July 26th, 2008

In order to get a feel for how long an exposure is actually useful, I’ve been capturing more Ha data for NGC 6888. The following image is composed of 71 10-minutes subs.

Ha filtered image of the Crescent Nebula (NGC 6888) - Version 2
The Crescent Nebula (NGC 6888) – Version 2

Imaging Equipment: WO ZS 80 II ED, DSI Pro II, Razorback Cooler, Baader 7nm Ha filter, WO 0.8x Flattener II
Guilding: Orion 80mm ST, DSI Pro
Mount: CGE

The majority of the difference in appearance between this image and the one previous post can be attributed to a slight tweak to the image’s gamma. When they are displayed with the same settings, there is a very slight decrease in the noise apparent in the darker areas of the newer image, at least I think there is. I’m not certain I could tell the difference if I did not know which was which.

Here is the previous image with the same (approximately) gamma tweak.

Ha filtered image of the Crescent Nebula (NGC 6888) - Version 1 with gamma tweak
The Crescent Nebula (NGC 6888) – Version 1 with gamma tweak

The Crescent Nebula (NGC 6888)

July 24th, 2008

I’m still having some problems with the guiding camera connection randomly failing, but overall the imaging setup is working fairly well at this point.

The following image was taken last night (July 23rd, 2008). It is composed of 29 10-minute exposures taken with Baader Ha filter.

Ha filtered image of the Crescent Nebula (NGC 6888)
The Crescent Nebula (NGC 6888)

Imaging Equipment: WO ZS 80 II ED, DSI Pro II, Razorback Cooler, Baader 7nm Ha filter, WO 0.8x Flattener II
Guilding: Orion 80mm ST, DSI Pro
Mount: CGE

Something to Post

July 23rd, 2008

Three months have passed without any images worth posting. During that time I’ve had multiple problems with the telescope setup that I’ve just recently resolved—if I’m really lucky they will remain resolved.

The first problem was an issue with the USB cables connecting the laptop to the cameras. DSI Pro/DSI II Pro cameras, at least with my laptop and hubs, like really short cables—anything longer than three feet between the hubs and the computer result in intermittent connection failures. The cables between the hubs and the camera must also be relatively short—anything over 6 feet and it is back to intermittent connection failures. My current configuration has a different powered hub for each camera, and no hub (regardless of whether or not the hub is connected to a camera) has more than one device attached. Any attempt to connect multiple devices to a hub also results in intermittent connection issues—even if the devices in question are two serial ports.

The other major issue has been with my homemade stepper-based motorized focusing add-on. The first attempt used the 10:1 gearing built into the focuser to get an acceptable step size out of a 200 position stepper motor. Unfortunately the 10:1 unit slipped too much to be useful. The second attempt used an small geared stepper attached to the main focus shaft via two timing pulleys and a timing belt. Unfortunately the stepper was too small. The third attempt used a 50 oz-in geared stepper motor with the same attachment method as second attempt. This is currently working reasonably well, although I do need to increase the backlash compensation a bit.

Lastly, I’ve been having problems with very elliptically shaped stars. The problem appears to be mostly resolved. I believe that it was due to the scope being incorrectly balanced.

I still have a drift in the images that I believe is due to flexure in the focuser. Short of a new focuser I don’t have any good idea for fixing this issues, at least while leaving the ability to actually use the focuser as it was intended. Most likely a new focuser will eventually be purchased.

Below is an Ha filtered mosaic of the eastern portion of the Veil Nebula (NGC 6995) composed of three different images taken over two nights. Each image consists of about 18 10-minute subs.

Ha filtered image of the western portion of the Veil Nebula (NGC 6995).
Eastern portion of the Veil Nebula (NGC 6995)

Imaging Equipment: WO ZS 80 II ED, DSI Pro II, Razorback Cooler, Ha filter, WO 0.8x Flattener II
Guilding: Orion 80mm ST, DSI Pro
Mount: CGE

Changes

April 26th, 2008

Since it is galaxy season, and due to the fact that narrow band filters really don’t do a thing for galaxies, I’ve decided to try capturing some variable stars. The don’t make very interesting images, but they do make interesting graphs once the images are reduced to photometric data and plotted. The first one up is XY Leo, as it has a very short period, which means that one night’s worth of data should show an unambiguous result.

Below is one of the images showing the object star (XY Leo), the reference star and the check star.

Image showing object star (XY Leo), reference and check star selections.

Below is the resulting photometric graph computed from all of the images. The blue line shows XY Leo, and the dark black line shows the check star. While there is a lot of noise, the resulting graph makes the variability of XY Leo very easy to see.

Graph showing variability of XY Leo during a three hour period.

As the images used were taken without any filters, the data is not really useful to anyone. As such, a photometric V filter has been ordered so that I can gather data that would be useful to someone.

It’s Dead, Jim

April 4th, 2008

This is what failed:

Another dead microswitch

A simple microswitch for detecting when the water collector is pulled out of the dehumidifier. It is the second microswitch in a consumer device I own that has recently failed. Someone should be spending an extra ten cents on a slightly better grade of microswitch.

By a Nose

March 23rd, 2008

My final image of the Horsehead Nebula (IC434, B33) for the year. I was hoping to add another couple of hours worth of subs, but it was not to be as the last set of images were taken after the camera had been removed and reinstalled. I’ve never been able to get the camera to align along the same plane as before when reinstalling the camera. This error causes the images to fail to align correctly, and is part of my problem with stars in the images appearing slightly elliptical in shape.

HorseHead Nebula (IC434, B33) in Ha

Imaging notes: guided, 41×600 seconds, ZS 80 ED II, DSI Pro II with Razorback cooler, Ha filter

Horsing Around Again

March 10th, 2008

The following image is composed of 24×600 second subs, Ha filtered, taken on March 9th and 10th. It has much less noise than the previous image. It will be interesting to see what happens with another couple of evenings worth of subs added.

Horsehead Nebula (B33, IC434)

Horsehead Nebula (B33, IC434) – Ha filtered

Part of the noise in the previous image was due to a shortage of darks – increasing the number of dark frames did reduce the noise greatly.

A Horse is a Horse

March 6th, 2008

Of course, this is the Horsehead nebula (B33, IC434) in the constellation of Orion.

It was imaged over two evenings, after several days of frustration with flaky mount and camera connections. I was hoping to capture more data this evening to help decrease the noise, but it turned out to be unexpectedly cloudy, so the camera is taking darks instead.

Horsehead Nebula (B33, IC434)

The above image is composed of 50×5 minute subframes taken with a Ha filter, dark and flat field calibrated, and DDP applied.