Last updated: 22 June 2005
Subject: DSI Pro - First Impressions Sent: Sunday, June 19, 2005 11:55:57 From: Stephen Bird (email@example.com) One for the astrophotography / Meade DSI folder. I did give Meade a hard time for their past sins, but the DSI Pro goes someway to redeeming them. So I thought I better offer some constructive comments on first light. First Light DSI Pro When the Meade LPI first came out, I bought one and the pictures it produced were fine as long as you stuck to the Moon and planets such as Jupiter and Saturn, beyond that was either hard work or just not practical. Still it was a good product and nothing on the market could compete on price and features. When the original DSI came out, I bought one of those as well, and had no end of trouble with it, in the end returning it for a refund. I seriously questioned whether I would buy a Meade CCD again. I was spoiled during a study week in Mallorca at an observatory with 7 LX200 GPS telescopes and SBIG research grade CCD's. I was tempted by Starlight Xpress cameras, and even considered SAC CCD's for a short while, but the price and software was the real turn off. They use similar CCD's, but for 3 times the price, whilst you get Peltier cooling, the software does not look that great, and Maxim DL is going to set you back another $400 on top of the camera prices that start at $1,000 and go up to the price of a family car! Well I took the plunge and bought a DSI Pro, you can always get a refund or replacement (well maybe) from Meade if the thing fails, and it looks like Meade has improved the quality control, as this imager didn't suffer from the dead pixels as did the standard DSI and LPI that I experienced previously. Dark frames produced usable results with only single pixels artifacts and even at 2 seconds exposure, 20 Deg C, no saturated pixels. With careful assessment of exposure times, and dark frame subtraction, there is no reason to suffer saturation problems. The software with the DSI Pro even includes passable manuals, unlike the LPI and original DSI, and with a few clues from the MaximDL help files, even the Image Processing package is usable. Teething troubles were: The Image Sensor window had dust and grease on it that needed cleaning - Despite protestation by the supplier, that you could "remove the IR filter" for cleaning by unscrewing the nosepiece, fact is you can't, on the DSI Pro. The lower body section of the DSI Pro is completely different. It is a black and white camera, and the filters (IR, Red, Green and Blue) are carried in a sliding cartridge, that runs through guide that is screwed to and so part of the lower body section of the DSI Pro. The nosepiece then screws into this. What I think caused the problem, was the slider had dust on it, and sliding it in and out of the guide, deposited the dust on the imaging chip window / cover slip. The grease was left over cutting oil on the threads of the guide, into which the nosepiece screws. Tip 1 - Before first use clean the threads carefully to remove the oil and clean everything to remove dust. Keep it clean! The dust was easily removed with a puffer from my telescope cleaning kit, the oil left 6 or 8 visible specs (splodges) on every image, and they were present even when the camera was focussed. Having got no joy from the supplier or advice from Meade, neither of which seemed to know the difference between the original and the Pro DSI, I checked the Sony website for the Exview HAD imaging chip the DSI Pro uses. Their advice was to use antistatic precautions, in a low dust environment, and clean the imaging chip cover slip with a cotton bud and isopropyl alcohol. Well I used the cotton buds, but some of Dr Clays telescope cleaning fluid from a batch I mixed up to clean the scope last time it needed it. One moistened cottton bud and gently wipe the cover slip over the chip. Then buff GENTLY with further cotton buds until clean. Six cotton buds did the job. Tip 2 - Only use 100% cotton, buds, and have the camera plugged in and displaying an image on screen. I used a blank white wall. As you remove the smear of cleaning fluid, the picture becomes clearer. You can easily see when the cover slip is clean, when the picture is clear and even. Change the cotton buds often, or you reapply the dirt. Tip 3 - Screw the filters into the slider, and leave them in there, keep them and the camera in a dust free box. The filters are hard to get in and out of the slider tray, and you will end up transferring dust to the camera or getting oily fingerprints on the filters. Only if you are using alternate filters, take them out. Better still consider a more sophisticated filter cassette. Focussing - Forget parfocal eyepieces! Unless you have an eyepiece extender tube, you won't make a Meade eyepiece parfocal with the DSI Pro. The reason is that the filter slider guide moves the camera another 1/2" away from the eyepiece port, so the point of focus is higher up. So either get an eyepiece tube extender or use a Hartmann mask, or one of the other methods of achieving focus. I was shown a great way of confirming sharp focus using FWHM (Full Width Half Maximum) in MaximDL, I have not tried it with Autostar IP yet, must dig out my observing log and try it! Sharp focus is always hard with the ETX electric focusser, and manual focus will have the image jumping all over the place. Trouble is even the slowest speed setting on the electric focusser is too fast. If you are confident enough with a soldering iron, break the focusser open (warranty now void!), find the red wire to the motor, cut it in half, and insert a potentiometer, 100 ohm preset type, with a bypass switch. You can then set yourself up, an ultra fine set of focus speeds along with the standard set, switchable between the two sets with the bypass switch. The real beauty of the DSI Pro is the drizzle software, from a 510 x 492 pixel imaging chip, you can use one of three processes: Drizzle Resolution Extended View Pixel Fraction; To either increase the picture size maintaining resolution, increase resolution same size, both, and probably a couple of other combinations. Must admit I haven't tried them all yet, but what I have seen so far is impressive. Tip 4 - Once you start using drizzle, the image file sizes in KB get bigger, up to 10MB, so you need maximum processing power and RAM on your PC. Wasting it running stuff that is not essential could mean lengthy waits for images to download or begin to appear in the combined view. Set up a profile for your PC that switches off anything non essential, e.g., SETI, screensavers, etc.,. make sure you have USB 2. If you are using a laptop that has USB 1.1 built in, get one of those USB 2 PCIMIA cards for $50. For a desktop, a USB 2 card is even less money. As you are imaging in B&W, you will be shooting 4 runs, combining images in LRGB. So you need to plan well and work hard imaging. If you have Maxim DL or can get the calibrate, combine and merge features working on Autostar IP, then you can save all raws images and do the crunching after the imaging session. Well I am still practising and in the UK, the light nights mean that virtually every thing is washed out by blue night skies, worse still when the Moon is in the way, during June and July, so I have nothing worthy to post at the moment. But that does mean I can practice in daylight, the Moon, Jupiter and one other really good feature is that you can run the drizzle process on old images (if you saved all images), so I will take a trawl through my 2GB of archives to see if there is anything I can do to improve on what I already have. For the future something interesting! When cleaning the DSI Pro imaging chip cover slip, I actually took the filter slide guide off the DSI Pro body, (Four screws, take care one is longer than the others so make a note of where each came from). Then opened the body itself up, (Four hex bolts, take care, there is a plastic gasket inside that needs correctly locating when you reassemble, and you must use antistatic precautions of course). The circuit board with the imager chip is fairly simple, the imaging chip cover slip can be cleaned without opening the body up, but I wanted to check to make sure! Now the interesting part, the heat sink fins on the upper body are cast in one piece, inside the upper body is a protruding square post, it is connected to the underside of the imaging chip with heat sink paste. First it would not be beyond the wit of man to replace that upper body with a Peltier cooling device to reduce dark current. Meade could easily do this no doubt. And after several hours of testing, those fins were warm to the touch. Second on the circuit board was a multipin connector that looked like it was there for some other future reason, intriguing! Any guesses anyone? Have fun, and as always, don't open the Meade items up unless you know what you are doing and accept that the warranty will probably be void when you do. Regards Stephen Bird
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