Cosmos Safari
The Cosmos Safari podcast co-hosts David Farina and Rob Webb take listeners on a journey to explore the depths of science's current understanding of the cosmos around us. The Universe is closer than you think!
Cosmos Safari
Discover the Power of f/2.2 Astrophotography - the RASA Telescope
Can you imagine capturing the cosmos in stunning detail without the hassle of long exposure times? Say hello to the RASA telescope, a game-changer in astrophotography! Join us on this enlightening episode as we sit down with Dave, our special guest, who breaks down what makes the Roe-Ackerman-Schmidt astrograph an essential tool for both seasoned astrophotographers and curious beginners. From its innovative design that positions the camera at the front to the ultra-stable focus system ensuring razor-sharp images, Dave explains how the RASA's F2.2 aperture revolutionizes how we capture the night sky.
Explore how the RASA's shorter focal length and faster imaging capabilities are perfect for places like Pennsylvania, where clear nights are a rare gem. Discover the different sizes available to suit various budgets and how each model doubles the amount of light gathered, making it a versatile choice for anyone passionate about stargazing. With Dave's expert insights and practical tips, you’ll learn how the RASA telescope can elevate your astrophotography game, making those fleeting moments under the stars a lot more magical. Don’t miss out on this episode that promises to transform your starry-eyed adventures!
Check out the video version of this podcast on the Cosmos Safari YouTube Channel www.youtube.com/c/cosmossafari
The kind of cool thing about the Rasa design is because it's collecting light so fast you actually don't need to be guiding always. You can get away with normal sidereal tracking in most cases.
Speaker 2:Well, dave, thanks for bringing me out here. You brought me out here to check out this Rosascope. Now, I'm no expert in the Rosascopes, but from what I know, from what I've read, is that this is the type of scope that you want to get if you just want to do astrophotography, right.
Speaker 1:That's right. This is a telescope that you actually cannot look through. It only can be looked through by a camera, and the place where the camera goes is kind of different, in that it's up at the very front, in the prime focus position, as opposed to behind the telescope's mirror, at the back, like you would normally see on like a Schmidt-Cassegrain. Now, this is the Roe-Ackerman-Schmidt astrograph. That's a mouthful it is. It is the RASA, and the kind of crazy thing about this is just how fast it is.
Speaker 2:It's an F2.2 telescope, which, so that means like mostly like an SCT. I have a Schmidt-Cassegrain, it's like a 10 or 11-inch one, and that is an F10, right, and this is an F2.2, so what does that mean?
Speaker 1:So, basically every time you change the F ratio by basically doubling the amount of light. Now, because we've gone very many F ratios, it's extremely fast when it comes to imaging and that's because the focal length is that much shorter, that's right.
Speaker 2:So it's about the same size aperture, but the focal length is that much shorter, that's right. So it's about the same size aperture, but the focal length is shorter, so you can get more light. That's right.
Speaker 1:So this is only 620 millimeters of focal length. An equivalently sized Schmidt-Cassegrain is at about 2,800 millimeters of focal length. The way you calculate the F ratio is you take the focal length of the telescope divided by the aperture of the telescope. So for this telescope you would take the focal length of 620 millimeters and divide it by the 279 millimeters of the aperture.
Speaker 2:Okay, so that gets you the 2.2. That gets you the 2.2. So, in other words, compared to my SCT of a similar size, less exposure in order to get the same amount of light and picture. Exactly Right.
Speaker 1:Yep, and so you know, for us here in Pennsylvania we don't get a whole lot of cloudless nights, yes, and so that time that you have is at a premium. And when you have a Rasa telescope, which does come in three different sizes for three different budgets, right, it comes in the eight inch, this is the 11 inch, and then there's a 36 centimeter version, which is approximately 14 inches, right, right, okay, and with each of those you get from the eight inch to the 11 inch, you're getting about double the amount of light gathering power, and that's just because of the aperture, and that big step, you know, also gets you that faster image, okay.
Speaker 2:So then, what about the focusing? I hear there's something special about how you focus on this thing.
Speaker 1:Right, this is the V2 version and it has the ultra stable focus system, which basically means that the mirror in the back here is kept very, very Much in place when the telescope is in motion. So if you're looking at one place in the sky, you move to a different place in the sky. The Position of the mirror stays the same. Now, if you remember, in like a Schmidt-Cassegrain, the mirror is actually what is moving to achieve focus. Okay, the same thing is happening here in the RASA telescope. The mirror is in motion to get focus, but the ultra-stable focus system allows it to stay in place in a very, very rock-solid way.
Speaker 2:In this one, the light's coming in, bouncing off the mirror, going through some optics here, bouncing off the mirror and going up to the camera that's up there, correct Right now. Can that take any DSLR or any type of camera or what it has?
Speaker 1:a T adapter which can be adapted to your DSLR camera, mirrorless camera, and then there's a separate adapter, that is, a 48 millimeter threaded adapter for your astronomical cameras as well. So, yes, you could have all of the different types of camera. And here we have your Canon full-frame, which it can handle. That, which is pretty incredible, that it can handle a full-frame camera. Not all telescopes can do that. This has a very no-transcript.
Speaker 2:And the camera's not actually going to be blocking that much of the light, right? Because it already has the sensor up there that's blocking some of it and the camera just adds like a little bit. It's not actually going to come out in the pictures, right?
Speaker 1:Right, and even in a Schmidt-Cassegrain you would have that central obstruction as well, and Newtonian's the same way.
Speaker 2:So let's say I actually go out and get something like this Jesus, Sorry about the chickens.
Speaker 1:If you're hearing chickens in the background, we uh, we're out at the farm right now. Yeah.
Speaker 2:Yeah.
Speaker 1:Getting a nice dark skies right, you gotta sacrifice some things.
Speaker 2:So let's say we go out and and, and let's say I buy this thing. What kind of mount do I want to put it on, or what kind of mount can I put it on? So of course, with the 11 inch you are going to need a pretty substantial mount to place this on. Um, but the kind of mount can I put?
Speaker 1:it on. So of course with the 11-inch you are going to need a pretty substantial mount to place this on. But the kind of cool thing about the Rasa design is because it's collecting light so fast you actually don't need to be guiding always. You can get away with normal sidereal tracking in most cases and that's nice because you can have a little bit less mount as a result. Now the weight capacity of the mount needs to be correct for the scope you have. The bigger the scope, of course, the larger the telescope mount, but the Precision of that is not required as much as it would be in a normal telescope, especially with an F-10 telescope like a Schmidt-Cassegrain.
Speaker 2:Now you're saying that this has a very wide field of view. So is this something that you don't want to use for really small stuff, or can you still use it for that really small?
Speaker 1:stuff collecting so much light. The kind of amazing thing is you can put very high megapixel cameras on the telescope and still collect enough light even though those pixels are very small, and so you effectively can digitally zoom in. So you're right in there are better options for very small objects, but you can actually get a pretty impressive digital zoom cropping in even with this very wide field. Maybe, if we have a chance, we could start to do some of the asteroid searching for ourselves. Right, We've got a pretty capable telescope here and maybe we can discuss trying to get some of the software capable to start looking for asteroids on our own.
Speaker 2:That would be quite the trek. Well, yeah, this is the first time I've actually seen Rasa and it's really cool. You know, upgrade from an SCT and I'm actually looking forward to hanging out with you a bit and taking some pictures. I'm looking to see what.
Speaker 1:I can get, and now that we'll have some time this summer, hopefully we have some nice clear skies and out here on the farm we have some really dark skies. We can see some Milky Way, and even though we can see Milky Way and it is that dark, I cannot even get away with a 30 second exposure because it is so overexposed, which is incredible Nice.
Speaker 2:That's fantastic, so it's going to make it make a really good scope for these guys.
Speaker 1:And we'll have to come back and show you guys what an image looks like through this telescope in the months to come.
Speaker 2:Yeah, looking forward to it.
