image size HP HD 4110

[rick olson]

hello folks. i am new to astrophotography and am looking into televue barlows. 2x and 3x i have an old C8 "orange tube" and an HP HD 4110 to get started. i have looked every where to find the pixel size in microns of the sensor and can't find a thing. does anyone know off hand what the size is? HEEEELP! lol. thanks!

[vlaiv]

Maybe easiest way to do it is to measure it if you can't find tech info on the sensor?

Don't mean measuring actual pixels - you can put camera in prime focus, or use one of your barlows, but it's probably better to do it in prime focus, if barlows are not telecentrics (powermates) - they can have varying magnification factor based on distance to the chip - prime focus is your best bet, since scope FL should be fairly accurate.

Measurement is simple - do a recording of a known object - maybe a planet, or better yet two stars of known positions (you can look that up in any planetarium software - for example Stellarium has angle measure tool). Pick two reasonably bright and close stars (don't use double star - that is quite close) - ones that you can identify, that are about half FOV to 3/4 of FOV in distance - and do a recording of them - even single frame is good.

Measure distance in pixels with any software that can measure distance between points on the image, and in planetarium software measure angular distance between chosen stars. Divide the two and you'll get pixel scale. From FL of scope and pixel scale, you should be able to work out pixel size to use further for calculations (or what ever you may need).

You'll probably need to round the value that you have - if you've got for example 2.3984, then it's obvious that pixel size is 2.4um (and something tells me that you'll find that your web cam has that pixel size).

[rick olson]

cool. that sounds like a good way to get it close to what i need. thanks for the quick reply!