Astro Tutorial #1.6: THE F-RATIO "fast" vs "slow" scopes - V2.0 enhanced audio quality

[@drandrewclarke]

I certainly second the comment that this series deserves more views. trust me, I have been trawling KZbin to find such a series and these tutorials are by far the best. have bought a zwo planetary camera and the instruction manual assumes you are anything other than a beginner. thanks

[@catchingphotons]

Thanks for those heartwarming words!!

[@mohammadrezahazhirpasand6148]

Amazing series of Astro! Many thanks. So far, this is the best series of learning vids on entire KZbin - for me at least.

[@catchingphotons]

Thank you VERY much for your support. Comments like yours keep me going! Clear skies my friend!

[@terryc47]

Thankyou, clarified F ratio's for this beginner. Certainly have a clearer understanding

[@catchingphotons]

Thanks fantastic! Always delighted to hear that my videos are of any help! Clear skies!!

[@brent3951]

This series is very well done! Thank you! I'll be telling my friends about it.

[@catchingphotons]

Thanks Brent! I appreciate your encouraging comment!!

[@z4zuse]

Excellent. Thanks. On to the next video

[@catchingphotons]

😉👍

[@eloniewordan8890]

This deserved more views!!! I am lucky I just bought a RASA 8 blindly for starting lol. After watching this I feel good.

[@catchingphotons]

You bought a RASA for a start? ;-) expect a steep learning curve!! Ask me whenever you need help - what mount do you have? Clear skies!!

[@eloniewordan8890]

@@catchingphotons yes I did, because it looks nice. I looked up online and I saw one KZbinr use it. And f/2 sounds cool tho I didn’t total understand what it is before watching this. I bought it with CGEM 2 mount (the Ota+mount combo), I also bought the ASI whole set because it has a deal with ASIAIR pro, 294MCPRO, and WiFi extender, 120mini guide scope camera, I also bought a cheap guide scope from Amazon.

[@eloniewordan8890]

Basically I bought the equipment I see other youtuber uses or recommended. And I am waiting them to be delivered at the moment.

[@eloniewordan8890]

@@catchingphotons yea I expect a steep learning curve but it’s ok. I see most of reviews for RASA 8 are good so I am not worried about it too much.

[@catchingphotons]

It's a great scope!! You'll have a lot of fun with it an I'm looking forward to seeing your images! Please post (Twitter) and tag me! Clear skies!!

[@kristiankrekac1112]

1:15 I don't understand this areal luminosity what is it. It's from the surrounding around a star? The background around it?

[@catchingphotons]

There are two possible ways to measure brightness. If you have a point-like source you can measure how bright this pixel on your sensor gets (lux). If you image a nebula or galaxy you can sum over all the pixels correlated to this target and give the brightness per area (lux/m^2). Point like sources gets brighter if your aperture increases because there is more light from this target getting onto the pixel. Areal luminosity gets brighter if your focal length decreases. F20 will give you less areal luminosity than f4 (keeping the aperture constant) because you cover more sky over the sensor hence more light will hit certain pixels. Faster scope = brighter image

[@kristiankrekac1112]

@@catchingphotons ​ @catchingphotons If I understand it right, with longer focal length the FOV is smaller so the light that would reach the sensor from the surrounding can't reach it? ( In your focal length video you used a paper roll for an example). Sorry for late response.

[@SiddharthMathur2k007]

There is an important thing that this video fails to mention. It is that the rather dim image in a slow telescope is not due to fact that it collects light slower but because of the higher magnification (read light distribution over a wider area) and the narrower field of sky it captures. So, slower telescope may take longer to produce an image but it will give you a lot more detail (due to magnification) of an object. 1:47 Also, this is incorrect. Light collection doesn't depend on f-ratio. It depends on aperture. 3:00 This comparison is misleading. If we keep the aperture fixed, the f/5 will produce a more magnified image (and thus dimmer).

[@manuelmira1216]

You should review this video for a better understanding. The light by the time ratio of a telescope is only dependent on the aperture and that's why a 8" inch telescope F2 or F10 have the same specifications regarding max star magnitude. The problem is the field of view (FOV) of the pixel of the camera. An 8" F2 for a given camera has a FOV of 1,25 arc second per pixel while an 8" F10 has only 0,25 arc second per pixel. Therefore the light (electrons registered in the camera) in an F2 pixel is distributed by 25 pixels in an F10 (a square of 5x5 pixels to get to a FOV of 1,25 arc seconds). So if you want your F10 to have more "speed" getting electrons per pixel and reducing resolution, you only need to increase the size of the pixel (getting a coarse camera) or post-processing with binning (not as good due to camera read noise). But besides this small remark, the video series is very good!

[@texdoms]

That clarifies it! Thanks.

[@catchingphotons]

You are very welcome!! Clear skies!

[@selfworthy]

Ohh, zum Glück ohne Trinkgeräusch! Vielen Dank, viel besser!

[@catchingphotons]

Those drinking sounds will forever be a running gag in this comment section ;-) clear skies!!

[@jesuschrist2284]

And the truth. Lol +1 sub ty

[@catchingphotons]

Thanks 😊!!