Copyright (C) 2004 Cloudy Nights Telescope Reviews
Meade DSI: Deep Sky Astrophotos Your First Night Out?

by Suk Lee

An imaging revolution from Meade?
Take Pictures Just Like These Your First Night Out proclaims Meades beautiful full-page color ads for their new Deep Sky Imager (DSI) CCD camera. The ads show impressive pictures of M20, M51, NGC891, etc, all for the VERY tempting price of only $299. The fine print below the pictures says All images were taken with a Meade 8 LX200 GPS using Meades Deep Sky Imager. How capable is the camera and can you really accomplish picture like those the first night out? Ill cut the suspense the answer is definitely yes, but theres a little fine print of my own. Read on

What's in the box?

The DSI comes with (clockwise from top left): - DSI camera body - RJ to DB9 adapter - eyepiece parfocalizing ring - Autostar Suite CDROM - Quickstart instructions - 4 wire RJ cable - 6 wire RJ cable - USB cable Everything you need to use the DSI is supplied in the box, including a built-in IR filter. The camera body is a nicely machined block of metal with a standard 1.25 nosepiece, threaded for 1.25 filters. The nosepiece unscrews to reveal the unusual IR filter sitting below the nosepiece. Unlike a regular 1.25 or 2 filter, its a flat disk of glass with a rectangular IR block area that fits over the CCD sensor. The quickstart instructions warn to remove the nosepiece carefully, as the filter is loose. If you plan on taking the filter in and out a lot, you might want to invest in a regular 1.25 screw-in filter for the front of the nosepiece. The specifications say that the sensor is a High Sensitivity Sony Super HAD Color CCD, and specifies the pixels as 9.6x7.5 microns, in an array of 510 x 492 pixels. The use of the HAD CCD is good news as they are known to have good sensitivity with low dark current (thermal noise). The pixel size is larger than the ones in the ubiquitous Philips TouCam Pro, so its not the same sensor, although from the same family of sensors. Exposure time capability is listed as being from 1/10,000s to 1 hour. One of the benefits of the Meade ground-up design, rather than modifying an existing webcam, is that long-exposure control does not necessitate a separate parallel cable everything is controlled through one convenient USB cable.

Autostar Suite Overview

The Autostar Suite software package that comes with the DSI is a combination Planetarium/Telescope Control/Imaging Acquisition/Image Processing system. As I do not have a Meade telescope, I only evaluated Autostar Suite's image acquisition and processing capabilities. Software installation is straightforward. Pay attention to the numerous warnings not to re-boot your computer until the very end of the installation. Also noted in various on-line forums was some difficulties with USB ports, etc. Immediately after installing the software (Dec 2004) I installed the latest patch from Meade, obtained from their website, and experienced no problems. After installation of the software you attach the camera to your USB port with the supplied cable (which is a little on the short side) to complete the hardware driver install process. Launching the software brings up the following screen:
Clicking on Image -> DSI Imaging brings up the image acquisition window:
Going clockwise from upper left the major functional areas are: - camera controls for exposure and gain control - image acquisition control area controlling how pictures are acquired and initially processed - image preview/viewing screen - Magic Eye Focus assist window - image contrast/brightness & histogram window
Autostar Suite - Capturing your first terrestrial image
Acquainting yourself with the DSI and Autostar Suite is easiest in the daytime where you have a bright stationary object. Select a terrestrial object far away enough from your scope that you can reach focus and select an object that has a bright glint on it. A reflection off of a street lamp, for example, is perfect. Focus with your eyepiece then remove the eyepiece and insert the DSI. They likely will not be parfocal so expect to have to refocus. The purpose of selecting an object with a bright glint is to be able to see something to focus on.

Make sure "LIVE" and Terrestrial are selected and click on "Auto Adj" to get the camera rolling. Autostar Suite will set the exposure to 1 millisecond then gradually increase exposure until you have a reasonable image and then stop. This can take a little time so be patient
Ignore the "Magic Eye" at this point and manually focus until you have a crisp image. I found the default image a little dim and manually increased the exposure time until I got a brighter picture. I also reduced the gain so that the brighter areas of the picture didnt burn out.
At this point youre set to head out under the night sky and focus on a star.
Autostar Suite Magic Eye focus assist
In my review of the Meade LPI, I covered the Magic Eye focus assist and didnt find it to be useful, recommending instead a Hartmann mask. Heres the section on using a Hartmann mask from that review. Note that the screen shots are slightly different because theyre showing the LPI window, but the principles are the same. Make a Hartmann mask, basically an aperture cover with two holes cut in it. As you can see from the picture it doesn't have to be particularly precise or pretty. For my larger telescopes Ive made permanent masks out of foamcore.
Start up Autostar Suite and get close to focus and then put the mask on your telescope. Instead of one star you now have two. As you get closer to focus the images will approach each other. As you get closer to focus the images will also get brighter, making it hard to judge exactly when they overlap.
Manually reduce exposure to reduce the brightness of the images and then bring them into overlap. You are in focus.
Once you've achieve critical focus on a star you can swing over to your object of interest.
First Light M1 with Mewlon 250 and 0.375x reducer
As the MSI is advertised as being suitable for an 8 SCT, I used a configuration which would give a similar focal length. I selected M1 as a reasonable first small DSO. I used a Mewlon 250 (3000mm prime focal length) and 0.375x reducer, the SBIG FR237. The FR237 is a 1.25 filter thread lens which conveniently screws into the nosepiece of the DSI. Equivalent reducers designed specifically for webcams are available from various manufacturers. The combination leads to a focal length of 1100mm, which is similar in focal length and therefore field-of-view to an 8 SCT with a 0.63x reducer.

Compare FOV with and without the reducer:
Step 1: Focus I selected Capella as a nice bright star and focused. Note that the LIVE window is all that was necessary with an exposure of 1 second, making it very easy to locate and focus on the star:
Step 2: Take dark frames Every CCD camera generates spurious electrical signal due to heat in the CCD. Fortunately, the accumulation of signal is very predictable, so its possible to take a set of dark frames (with the telescope capped) which are just the spurious signal and then subtract the spurious signal out of your images. In order for this process to work precisely, the CCD must be temperature controlled. The DSI is not, however if the ambient temperature is fairly constant, then a good approximation can be made by turning on the camera, letting it equalize to ambient temperature, then taking a set of dark frames just before image acquisition.
In Autostar Suite select Take Darks under the Image Process pulldown:
The window to the right will change to show the range of darks that will be taken by Autostar Suite and the total time, 8.5 minutes in this case. I left it to the defaults it came up with, and clicked on Start.
The software then thoughtfully reminds you to cap your telescope and click OK before really starting the sequence. Go have a cup of coffee When you come back, youll find that the Dark Subtract checkbox is now checked, and the program is reminding you to uncap your telescope. Youre set up to take long exposure pictures with automatic dark frame subtraction now:
Step 3: Frame M1 and set up a guidestar Finding M1 will be the first real challenge for that First Night Out. Even with a 1 minute exposure, M1 is essentially invisible. Plus, the field of view at this focal length is so small that star-hopping with the camera will be very difficult. This is where GOTO becomes a real life-saver. Focusing on that bright star also serves as a reference point for your GOTO telescope. I centered Capella as above, then instructed my mount to swing to M1. I set an exposure of 1 minute and clicked on Long exp and Preview. The Count Down window shows the time left in the exposure:
As you can see in the picture above, M1 is virtually invisible, but Im trusting that its in there somewhere. So, well get ready to take a bunch of exposures and accumulate them. Autostar Suite has a feature which they calling Tracking and which other manufacturers often call Track-and-accumulate. In this mode a succession of pictures are taken, aligned in realtime, and then summed in realtime. This feature allows you to take a set of pictures with the effective exposure of one long exposure, but without autoguiding. If you telescope is accurately polar aligned, then short exposures without autoguiding will be sharp enough to allow you to stack a bunch to increase the overall effective exposure. In order to align the pictures, you have to identify a star that Autostar will use to align successive pictures. Pick a bright star without any nearby neighbors to confuse the program (easy in this case!) and draw a box around it with the mouse as shown above. Autostar Suite will now use this star to align and accumulate frames.

Step 4: Start taking long exposures OK, Ill admit something, I cheated a little. I used an autoguider setup since I wanted to take long exposures of M1 (5 min) and I had a feeling that my mount wouldnt track accurately at 1100mm for 5 minutes. However, the test of Autostar Suites Track mode was still valid because there was still some frame drift because I wasnt autoguiding on a star very near M1. In other words, Autostar Suite still had to align frames before accumulating them. Heres the setup I used: 1) 2) 3) 4) 5) 6) 7) 8) Set up for 5 minute exposures Make sure Dark Subtract is checked Set up Image Process to Deep Sky Set Min Quality to 0 to force Autostar Suite to select and stack every exposure Set Evaluation Count to 1 for the same reason and make sure Combine is checked Put in the object name Click on Save Proc to bring up the popup and Set up to Save Every Composite Image
In normal operation, Autostar Suite will just save one composite image. However, since there are a lot of airplanes in my area, I didnt want to chance having an airplane fly through the frame and have its trail saved into the image. When Save Every Composite Image mode is set, every successive
composite (e.g. 1, 1+2, 1+2+3, 1+2+3+4, etc) is saved, so at least I have the previous images if a plane flies through the field-of-view. Heres the result after clicking on Start:
Note that M1 is now visible (GOTO rules!) and that Autostar Suite has drawn green crosshairs marking the position of the guidestar.
Heres the result of 13 exposures, 65 minutes of total exposure, straight out of Autostar Suite:
And heres the result after some histogram tweaking, color adjust and slight color boost in Photoshop:
Pretty impressive for a $299 camera and with most of the work done by Autostar Suite!
Second Light M42 with Megrez 80 and 0.63 focal reducer
At this time of the year, M42 is a great DSO object for initial imaging because its bright, large, easy to find, and spectacular to image. Because the DSI has a small imaging chip, a short focal length would be needed to get a decent field-of-view on M42. Doing the calculations indicated a desired focal length of around 300mm. Thats a LOT shorter than an 8 SCT focal length of 2000mm, and shorter than what can be achieved with an 8 SCT and 0.33x focal reducer (660mm). Fortunately, I had a Megrez80 achro refractor and Celestron 0.63x reducer on hand, which gives almost exactly 300mm. While the 0.63x isnt designed for refractor applications, because its also designed to correct for the field curvature of an SCT which is different than a short focal length refractor, the small image sensor means it will work well.
I also had the variable T to SCT adapter from the Meade 0.33x focal reducer handy, which is needed to get approximately the right spacing between the 0.63x reducer and the DSI. I Put it all together, slap onto the Megrez80, focus on a bright star, then swing over to M42 and compose. Again, a guidestar was selected and a series of pictures taken. Because the dynamic range of M42 is so great , I took a series of photos of 30 seconds, 2 minutes, and 5 minutes exposure, planning on compositing them together later. Here are the results, straight out of Autostar Suite:

16 x 30seconds:

4 x 2 min:

4 x 5min:

As exposure time increases, more of the surrounding nebulosity is captured, but the central area is burned out because its so much brighter than the surrounding areas that it saturates the CCD. In the 4 x 120s and 4 x 300s images, the burned out regions arent just white, they have an unpleasant mottled green appearance. To get a nice picture of M42, compressing the dynamic range of the image, I stacked the three pictures. On top, was the 4 x 300s image, with the burned out regions masked out so that the underlying image could show through. Underneath was the 4 x 120s image, again with the burned out regions masked out, and finally on the bottom was the 16 x 30s image. Each image was black point adjusted and curved to match the previous layer.
Its easier to explain with a picture:
The resulting image was then composited together, slightly histogram adjusted further in Photoshop and then Despeckled and Dust and Scratch Filtered and finally gently unsharp masked:

A very nice image.

Summary
At the beginning of the review I said you could get deep sky pictures out of the box in one evening. I certainly did. However, there are some caveats: my telescope was very well polar aligned I had a bunch of telescopes and reducers available to get different fields-of-view for some of the images I used a $3k autoguiding system (including scope) I have a lot of experience with astrophotography
I think, realistically, if you have never done ANY imaging, you wont be able to get comparable images your first night out. Its no fault of the DSI, its that theres just too much stuff to learn, polar aligning, just getting focus (which can take HOURS the first time you try it), and image post processing. However, for the price, this is the easiest introductory camera I have used, and is definitely capable of imaging virtually all of the Messier catalog with an impressive effort-and-cost-to-results ratio.
DSI likes: everything you need is in the box one USB cable control is MUCH simpler than competing parallel port assisted designs Autostar Suite track-and-accumulate works well decent sensitivity and noise immunity automatic dark frame mode

DSI dislikes: odd IR filter easy to damage standard 1.25 thread-on filter would have been better CCD isnt temperature controlled, but hey, its only $299 no obvious ways to automatically do flat frames
Bottom line Meade has set an impressive, new, low price point for entry level color DSO imaging. If you want to dabble, this is a great way to start. Click to Discuss this article in the forums