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bobro

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About bobro

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    Star Forming

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  • Location
    Isle of Wight
  1. bobro

    DSS trails

    It does look as though alignment is using hot pixels - the 2 hot pixels taken as examples in the stacked image and single sub are in the same place:
  2. bobro

    DSS trails

    DSS doesn't like out of focus stars and may ignore them. The result can be registering on camera hot pixels instead, with the result of trailing showing if true stars move slightly between each sub. You can test for this by reducing the sub resolution by 2 in each x,y direction before stacking - doing this in jpeg (not ideal for imaging) if necessary. Reducing the resolution makes stars tighter and DSS may then stack correctly.
  3. bobro

    Motor Drive Astrophotography

    My imaging effort started out with an EQ2 (Meade version with tubular legs) and Economy RA motor drive. With a modified Meade Polaris 130 (650mm focal length) scope mounted, exposures of 30 secs were typically achieved without star trailing, 60 seconds occasionally if I was lucky. The tiny speed control knob on the RA motor makes it tricky to set the speed so I fitted a larger knob. The more expensive motor (about £60) has a more accurate speed and so is easier to use, but I stuck with the basic motor to eventually modify the setup for dual axis guiding using 2 economy motors. The EQ2 was working beyond its design limits with the guided setup but it did work. The main drawback was lack of goto which can't be added to the EQ2 due to the DEC design, so onwards to an EQ5/CG5. Results on an EQ2 will depend on what you mount on it. Although the tripod wobbles if touched it settles down within a few seconds and so can be used for imaging. Here is one of my first attempts with the unguided EQ2 with Meade Polaris 130 using a mix of 45 and 10 second exposures.
  4. That's a reasonable scope and what I use for imaging, but there are a couple of issues as @alacant mentions: 1) Getting a DSLR to focus - a 2x Barlow isn't a great solution as it results in 4x exposure increase and doubles the focal length. As an alternative I cut 40mm from the scope tube. 2) The Meade Polaris 130EQ has a 1.25" focuser and coma correctors aren't readily available at that size. I made one from stock parts - not difficult. To give you an idea of what the scope can do, here's one of my first images (without coma corrector) taken with the Meade on an EQ2 mount with a simple 'clockwork' motor. Also a much later image (with coma corrector) where I changed the mirror for a used SkyWatcher 130P mirror (£30 and better quality) and mounted the Meade on an EQ5. HTH
  5. bobro

    Autoguiding system

    Yes, AstroEQ requires stepper motors and works with the SkyWatcher motors (amongst others). The SkyWatcher simple handset isn't used with AstroEQ - if the motors can be obtained on their own you could go straight to goto using AstroEQ, saving the cost of the simple handset.
  6. bobro

    Is this a problem with my flat frames

    The flat is totally black towards the corners and totally white at the centre. A flat needs to be an intermediate brightness level in order to correct an image. Perhaps a lower gain would help? I'm not familiar with the ASI1600mm or AstroArt, however DSS for example correctly applies flats even when taken with a different ISO to the main image.
  7. bobro

    Count The Galaxies

    Hey, that's a lovely image! Please post it for all to see, including your equipment specs and image details.
  8. bobro

    Autoguiding system

    Adding an AstroEQ as an upgrade (replaces the simple handset for the motors) will provide goto and guiding. Makes finding targets soooo much easier using goto.
  9. At this time of year and with an image of Markarian's Chain it's fun to see how many galaxies can be counted. This image from a couple of nights ago was 26 subs at 3 min, 650/130 reflector. The second image is an annotated version from astrometry.net - how many did you get?
  10. bobro

    Arduino Controlled Scope Fan

    Very neat assembly! Now the tricky bit - quantifying how much of a difference the fan speed makes. Cool down (up?) graphs would be interesting to see.
  11. Some comments that may help: The transistor is not in the correct place in the circuit - you want the transistor to saturate when operating as a switch. It should be between the diode cathode and ground. Similarly between the 47k resistor and ground. In practice the 47k resistor is not required as current is limited by the camera, so shorting the resistor will put the transistor in the correct place. When using a transistor as a switch don't use the current gain to try and work out resistance values. Just make the transistor saturate - perhaps changing the 2.6 Mohm resistor for a 100 kohm (or similar value). As you say, the grounds of the camera and PI must be connected together to make the curcuit work.
  12. A DSLR isn't likely to come to prime focus with a SkyHawk-1145. A 2x barlow lens would help with focus, but then the focal length would be 1000mm - a bit much if used with a lighter mount and exposures would be X4. I've recently obtained the same spec OTA (Konus make) and, in order to image with my DSLR, plan to try moving the mirror up the tube using long screws to start with, shortening the tube if screws aren't satisfactory.
  13. bobro

    What a b"£$%y stupid hobby.

    Perhaps I'm coming closer to understanding the purpose of the black tube in the corner of my living room ...........though there are 3 of them now (plus a little baby one perched on another). Could be a modern version of plaster ducks on the wall? I hope the numbers stop increasing - there may not be enough house room if any more appear during this cloudy weather!
  14. bobro

    What a b"£$%y stupid hobby.

    Not sure I understand what you are on about......or why I am responding to ths post. There is this strange black tube in the corner of my living room. I'm curious about what it is for though think the weather had some connection to what I did with it. Still, I grease it from time to time in case it comes in useful.....confused.
  15. bobro

    M51 2nd try, question..

    The guide report shows dithering - perhaps this has a direction bias?
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