[Tom Bishop]

First you claim that camera lenses are equivalent to astronomical telescopes, and have now discarded that argument in favor of a claim that camera lenses are telescopes. Sometimes the best thing to do is to just stop posting.

And so what? It's even more proof that you can use an EQ mount, if properly polar aligned, and with a $10,000 EQ mount with hyper precision motors and gears, way more precise (and expensive) than the models you reference, you can get some 4+ hours duration - Look at Rigel in the video, stays in frame the whole time. No software is going to pull something out of frame back into frame.

You keep repeating yourself. It could have just wobbled back and fourth, or he could have repeated it a number of times, adjusting the mechanisms until he got what he wanted to keep everything within a reasonable frame.

What part of the phrase in bold, "is left to track on its own and is unguided." do you not understand? What does, left to track on its own mean to you?

Software manipulation? How do you think any timelapse is made, whether based on video or photography?

I left my camera to create an exposed shot to capture on its own; that doesn't mean that I didn't try it a bunch of times, that I didn't go to great lengths to create artificially good conditions, or that I didn't put it through extensive editing to unnaturally make what I wanted.

[stack]

First you claim that camera lenses are equivalent to astronomical telescopes, and have now discarded that argument in favor of a claim that camera lenses are telescopes. Sometimes the best thing to do is to just stop posting.

I can attach a camera to a telescope lens and I can attach a telescope lens to a camera. How do you think someone with a telescope captures an image? Is that something that is too complex for you to understand? Not to mention, as already cited, the guy used a lens specifically designed for astrophotography and attached it to his Canon DSLR. So was his rig a telescope or a camera? Both. Why is this so difficult for you? And why are you trying to make some big distinction? It doesn't matter.

And so what? It's even more proof that you can use an EQ mount, if properly polar aligned, and with a $10,000 EQ mount with hyper precision motors and gears, way more precise (and expensive) than the models you reference, you can get some 4+ hours duration - Look at Rigel in the video, stays in frame the whole time. No software is going to pull something out of frame back into frame.

You keep repeating yourself. It could have just wobbled back and fourth or that he could have repeated it a number of times, adjusting the mechanisms until he got what he wanted to keep everything within a reasonable frame.

What part of the phrase in bold, "is left to track on its own and is unguided." do you not understand? What does, left to track on its own mean to you?

Software manipulation? How do you think any timelapse is made, whether based on video or photography?

I left my camera to create an exposed shot to capture on its own; that doesn't mean that I didn't try it a bunch of times, that I didn't go to great lengths to create artificially good conditions, or that I didn't put it through extensive editing to unnaturally make what I wanted.

He states, "is left to track on its own and is unguided." That pretty much says it all. Now you are just making up things. I could just as easily say, "It means he didn't try it a bunch of times, he didn't go to great lengths to create artificially good conditions, he didn't put it through extensive editing to unnaturally make what he wanted."

"is left to track on its own and is unguided." is just what it says. Why you're making up a whole bunch of stuff that he could have done is beyond comprehension.

[jimster]

"I've never seen a camera with an equally powerful lens as an astronomical telescope. Who knew that telescope manufacturers were unnecessarily making their telescopes so large when they could pack it down into a small package and get equal results, as indicated by someone's claim on an internet forum. " - Tom Bishop

The Hale telescope at Mount Palomar has no eyepiece. It is impossible to look through it as a telescope, all you can do is take pictures. Is it a telescope or a camera?

The pictures it takes require long exposures, thus an EQ mount is necessary. A large "horseshoe mount" has a motor on ti to power it at 1 rev per day, aka 15 degrees per hour. The mount is aligned to be parallel to the earth's axis. Look it up, really fascinating 1935 tech. Still used today by CalTech, UC, Cornnell, and JPL. The FAQ says "small conspiracy", but if the earth is flat they must all be some combination of stupid and/or liars.

All major astronomical telescopes use cameras, for at least 3 reasons. 1 - permamnent record for sharing and further study, 2 - film/digital can do long exposure for dimmer objects, the human eye can't, and 3- time on these telescopes is valuable, you submit request to take pic of something, they stack them up one after the other to get the most out of the telescope. I expect there is close to zero astronomers putting their eyes to a telescope and staring. Besides, they probably use spectrographs, infrared, ultraviolet, etc, to study things that are outside the wavelengths the human eye can see.

When mars was unusually close and thus the largest it ever appears, a local astronomy club had a public meeting where they lined up their telescopes from small to large, all with EQ mounts and 1 rpd motors. We looked through the eyepieces, smallest to largest, and each one you could see mars a little better. The last one had no eyepiece, it had a CCD that connected to a laptop through usb. So that telescope, you looked at a laptop screen. It used eq mount to get exactly the same image as the eyepiece telescopes, although bigger and more detailed.

I doubt that modern telescopes use film cameras any more. Why bother with developing and cost, just get a shareable permanent image in a file. Here are a bunch of digital cameras made to screw on to telescope eyepiece mounts:

https://www.highpointscientific.com/telescope-accessories/astro-photography/ccd-cameras

Telescope/cameras that are physically larger collect more light and so can see dimmer objects. This is why owls and other night hunters have big eyes. The only part of the telescope that can't be miniaturized with adequate results is the optics. You can make a tiny telescope/camera, but it won;t see very much. Your cell phone is a telescope, just set it to magnify. It's not a good one, but you can buy an external lens and make it betterm or even better, mount your cell phone to a telescope:



A telescope is, or can be a camera. A single lens reflex camera allows the photographer to look through the same lens as the film (or CCD) will see, with a telephoto lens , it is literally both a telescope and a camera.

[DuncanDoenitz]

I left my camera to create an exposed shot to capture on its own; that doesn't mean that I didn't try it a bunch of times, that I didn't go to great lengths to create artificially good conditions, or that I didn't put it through extensive editing to unnaturally make what I wanted.

What exactly are "artificially good conditions"?  Do you mean "with precision"?   

I have a precision timepiece.  The drawback is that it only tells the correct time if I set it with precision or, perhaps in your vernacular, "artificially good conditions". 

[astroman]

I'm not sure why you guys like to come here and keep trying to claim this in repetition, but it is a falsity. Unguided Telescopic Equatorial Mounts only work for a few minutes before drifting off of the target star

If what you say here is true Tom then how come when using my 10" F8 (f/length = 2000mm) RC telescope with a ZWO ASI290 camera (FOV= 0.16deg by 0.09deg) I can track Jupiter for over an hour without any danger of it drifting off?  What do we mean by 'drifting off' here... drifting out of the FOV completely or just drifting within the FOV which is quite normal for an unguided mount. An FOV of just 9.6' x 5.4' is not exactly huge is it so what is your point here?

The telescope is mounted on an AstroPhysics 1200GTO mount. My system is only set up for OAG (off-axis guiding) so I cannot guide the mount while imaging planets. I don't need to in any case. I have got the mount polar aligned to an accuracy of better than 30" off the true NCP by regular checks using a QHY PoleMaster camera which is specially designed for the job. The performance of any mount is dependent on how well it has been set up. I have known people to align their equatorial mount directly on Polaris itself. By doing so they are immediately creating a 40' error into the tracking performance of the mount. In which case it would drift off target a lot sooner. But that of course is a human error and nothing more.

Unguided equatorial mounts are capable of very short exposures, as indicated by my original sources. This falls in line with what was claimed.

The purpose of guiding is to correct very small errors in tracking performance over extended periods of time. Errors that are due to either mechanical imperfections in the mount (PE or periodic error) or errors due to the accuracy of the polar alignment.

What you appear to have done is to pick a particular tutorial from the excellent collection from Starizona. You have then taken the meaning of that tutorial completely out of context in order to try and make out that it is supporting your opinion that equatorial mounts can only track successfully for very short periods of time. If you take that tutorial as a whole along with the others on the same site you will quickly realise that it is not saying that at all.

For visual observing such small errors in tracking are unimportant and an unguided equatorial mount is perfectly capable to tracking a celestial body for extended periods of time without any need for any adjustment. Certainly within the same field of view. If the target drifts out of the FOV then that is down to errors in polar alignment rather than anything else. Astrophotography by its nature places much higher demands on the performance of a telescope mount for obvious reasons. You need to be able to keep every star (each a point source) in every image on the same pixels of your camera for several hours. You don't need anywhere near the same level of performance for visual observing. In any case how does your claim about the tracking/guiding performance of equatorial mounts help your claim about the Earth being flat? Or is it just a case of trying to satisfy your desire to be right all the time?

Also, unguided equatorial mounts are perfectly capable of tracking the Sun for solar imaging for extended periods of time. You just have to set the mount to track at the solar rate instead of the sidereal rate. You will appreciate that it is pretty difficult to guide a mount during the daytime when no stars are visible!

So equatorial mounts are very much fit for purpose and do what they are designed to do very nicely. I'm not sure what the point of all this is anyway in relation to anything to do with what shape the Earth is. Equatorial mounts have always been designed to work on the global Earth that we all live on. The mount has a polar axis which is lined up with the Earths polar axis. That is what polar alignment means.

A telescope pointed at a celestial object must change its angle at 15 degrees per hour to keep that object in the center of view.

Not quite. There are 24 hours of RA (celestial equivalent of longitude) and so 360 degrees / 24h = 15 degrees per hour yes. But the sidereal day, measured as two successive transits of the meridian by a given star (e.g. Mintaka since it lies just 16" N of the celestial equator) = 23h 56m 4sec. So since the sidereal day is just 4 minutes less than 24h so a telescope must track a tiny bit faster than 15 degrees per hour but the difference is very small indeed.

It's not exactly 15 degrees an hour. The celestial bodies change speed throughout the day.

This is definitely not my experience after 40 years observing the sky.  The RA and Dec of stars doesn't change during the day and the speed of the Earth rotating doesn't change so what speed are you referring to here?

I'm just trying to imagine how tricky astrophotography would be if the speed of celestial bodies was changing throughout the day (and therefore night as well I assume). Tracking would be an absolute nightmare!

I've never seen a camera with an equally powerful lens as an astronomical telescope.

When used for photography, how 'powerful' the system is depends only on the focal length of the telescope. The magnification of a telescope when used for visual observation is decided by the ratio between the f'length of the telescope divided by the f'length of the eyepiece. So for example when used with my 13mm Ethos eyepiece my 10" RC telescope (f'length = 2000mm) gives a magnification of 2000/13 = 153.8x.

When used for photography we obviously replace eyepiece with a camera so the telescope becomes the lens of the camera. You can get T adapters which provide the interface between the lens mount of a DSLR and the focuser of the telescope. So with such a simple adapter I can easily attach my DSLR to my 10" RC telescope. The telescope then becomes effectively a 2000mm mirror lens as far as the camera is concerned. What you lose in this configuration is any of autofocusing capability of the DSLR but astronomers can use other tools such as a Bahnitov mask to focus manually instead.

Here is an image (of the Rosette Nebula) that I have personally taken. It is an unguided 15 minute exposure using my equatorial mount.