Explore Scientific FirstLight/Purchase move!

[rickclark28]

Exhausted searching for new scope. Giving myself a deadline.
*I may just order the 102mm Explore Scientific FirstLight refractor and take my chances. Looks to me like it will be a very good starter for me.
*I really appreciate this forum and its members.
*MistrBagr has me excited about this FirstLight Refractor in 80mm or 102mm
*It is between the 80mm and 102mm Explore Scientific FirstLight refractor with the Nano Twilight Mount.
*Keeping the budget at $300.00 to $500.00 is limiting but I may have a good start with this one.
*Any thoughts .and. .or. feedback is welcomed.
Have a great day!
Rick

[SkyHiker]

The risk is low for that price. I have the Nano EQ mount, it is fairly stable for the price. With a focal ratio of 6.5 it should be a nice allround beginner scope. Explore Scientific has a wide variety of starter options providing good value. If you decide you like the hobby and buy something better later on you can still keep it as a travel scope. I would say, go for it.

[helicon]

That would be a good choice to start out. Good luck!

[Ylem]

Both the 80 and 102 look decent, f8 and 6.5 respectfully, that's better than the usual f5 IMHO.

Now you got me looking at the 102, it will give nice wide field, and less CA over an f5

[Lady Fraktor]

The 102 mm f/6.5 is a fairly popular small refractor here, they are actually made for Bresser (Bresser and ES have a partnership)
A nice telescope, I had the 102 mm for a couple of years and enjoyed it.

[Bigzmey]

Mount would be the weak spot. I believe Nano Twilight Mount is better match for 80mm and will be too shaky with 102mm. Nano EQ will provide better stability in the same price range.

[rickclark28]

I placed an order with High Point Scientific for the Explore Scientific FirstLight 102mm Doublet Refractor with EXOS EQ Nano Mount.
*It is on back order on many sites, so the wait begins.
*Thanks to all of you and MistrBagr for his FirstLight Refractor in 80mm prelim review.
*I will have many questions soon enough and hope to follow up on MistrBagr's continuing review. (good review and data!)

[helicon]

Good luck. I bought a Celestron 102mm XLT refractor from High Point in November. Ended up being delivered here recently. Originally they told me it would be out of stock until April 2023!

[SkyHiker]

It's a different one than the one I thought you referred to that I found on the ES site. The one that I see on HS has focal length of 1000 mm at F/9.8. I now see that ES has both a 1000 mm and 660 mm. Which one did you order?

The 1000 mm one is more for planets while the 660 mm is better for deep space. With the right choice of eyepieces it may be made to work but personally I would have preferred the 660 mm. Should you find out that you don't get enough light you may want to add an 80 mm F/5. I have used my ES ED80 with the Nano EQ mount, it was quite nice to use.

[SkyHiker]

You may need an extra counterweight, as I recall having to add one for my ED80. Luckily, I had one extra from a supermaket telescope. The ED80 has a bit more offset than the 102 mm on the picture, and a triplet is heavier than a doublet. FYI.

[rickclark28]

It's a different one than the one I thought you referred to that I found on the ES site. The one that I see on HS has focal length of 1000 mm at F/9.8. I now see that ES has both a 1000 mm and 660 mm. Which one did you order?

The 1000 mm one is more for planets while the 660 mm is better for deep space. With the right choice of eyepieces it may be made to work but personally I would have preferred the 660 mm. Should you find out that you don't get enough light you may want to add an 80 mm F/5. I have used my ES ED80 with the Nano EQ mount, it was quite nice to use.

The 1000mm one. Explore Scientific FirstLight 102mm Doublet Refractor with EXOS EQ Nano Mount.
*It is on backorder, and I have time to come up with a plan for the mount issues. I appreciate the feedback!
*I am getting excited to work on the eyepiece issues and selections as well. I have several sets of eyepieces from my father-in-law-> going to pull them out and see what's there. You mentioned the 80 mm F/5 above...do have a recommendation?

[rickclark28]

Good luck. I bought a Celestron 102mm XLT refractor from High Point in November. Ended up being delivered here recently. Originally they told me it would be out of stock until April 2023!

Thanks! Just received an update email. Waiting for manufacturer to provide lead time. So, no promise date as yet.
*I thought about the Celestron 102mm XLT refractor, but I do not know enough about the differences between them.
*My neighbor is still waiting for his Celestron 102mm XLT refractor from HP. He ordered it in November 2022. I am glad you received yours!

[rickclark28]

Again, thanks to all you guys/gals! The notes from MistrBagr on the 80mm really got my attention on this entry level scope in 102mm.
*I am so freaking excited I can't wait to move on with the project and set this up with my granddaughter (14yr.)
*Our neighbors have an Apertura10 coming up for sale in the spring so I will be looking at that too!

[SkyHiker]

It's a different one than the one I thought you referred to that I found on the ES site. The one that I see on HS has focal length of 1000 mm at F/9.8. I now see that ES has both a 1000 mm and 660 mm. Which one did you order?

The 1000 mm one is more for planets while the 660 mm is better for deep space. With the right choice of eyepieces it may be made to work but personally I would have preferred the 660 mm. Should you find out that you don't get enough light you may want to add an 80 mm F/5. I have used my ES ED80 with the Nano EQ mount, it was quite nice to use.

The 1000mm one. Explore Scientific FirstLight 102mm Doublet Refractor with EXOS EQ Nano Mount.
*It is on backorder, and I have time to come up with a plan for the mount issues. I appreciate the feedback!
*I am getting excited to work on the eyepiece issues and selections as well. I have several sets of eyepieces from my father-in-law-> going to pull them out and see what's there. You mentioned the 80 mm F/5 above...do have a recommendation?

My recommendation is to first use what you have got before buying more gear. That's because a novice's expectations are usually absurdly high. What you will see are fuzzy blobs, and not fancy pictures of galaxies. You have to get into the hobby, practice, then decide again if you like it enough.

About eyepieces, the longer the eyepiece focal length the more concentrated the light on your retina. The exit pupil of a scope with focal length F=1000, eyepiece focal length f mm and diameter D=102, is D*f/F. If your eye pupil is p=5 mm in diameter, we need D*f/F <= p in order for the exit pupil to not eclipse your eye pupil. That means f <= p*F/D = 5*1000/102=49 mm, so basically, you're good. Let's say your longest focal length eyepiece is 35 mm, that is a magnification of F/f=1000/35=29x. Another rule of thumb based on laws of physics is that the magnification should not exceed D, which means F/f <= D or f >= F/D = 1000/102 = 10 mm, so that's the useful lower limit of your eyepiece focal length.

[rickclark28]

It's a different one than the one I thought you referred to that I found on the ES site. The one that I see on HS has focal length of 1000 mm at F/9.8. I now see that ES has both a 1000 mm and 660 mm. Which one did you order?

The 1000 mm one is more for planets while the 660 mm is better for deep space. With the right choice of eyepieces it may be made to work but personally I would have preferred the 660 mm. Should you find out that you don't get enough light you may want to add an 80 mm F/5. I have used my ES ED80 with the Nano EQ mount, it was quite nice to use.

The 1000mm one. Explore Scientific FirstLight 102mm Doublet Refractor with EXOS EQ Nano Mount.
*It is on backorder, and I have time to come up with a plan for the mount issues. I appreciate the feedback!
*I am getting excited to work on the eyepiece issues and selections as well. I have several sets of eyepieces from my father-in-law-> going to pull them out and see what's there. You mentioned the 80 mm F/5 above...do have a recommendation?

My recommendation is to first use what you have got before buying more gear. That's because a novice's expectations are usually absurdly high. What you will see are fuzzy blobs, and not fancy pictures of galaxies. You have to get into the hobby, practice, then decide again if you like it enough.

About eyepieces, the longer the eyepiece focal length the more concentrated the light on your retina. The exit pupil of a scope with focal length F=1000, eyepiece focal length f mm and diameter D=102, is D*f/F. If your eye pupil is p=5 mm in diameter, we need D*f/F <= p in order for the exit pupil to not eclipse your eye pupil. That means f <= p*F/D = 5*1000/102=49 mm, so basically, you're good. Let's say your longest focal length eyepiece is 35 mm, that is a magnification of F/f=1000/35=29x. Another rule of thumb based on laws of physics is that the magnification should not exceed D, which means F/f <= D or f >= F/D = 1000/102 = 10 mm, so that's the useful lower limit of your eyepiece focal length.

Thank you so very much for this! The "About eyepieces" calc you provided makes perfect sense to me and I am grateful for you providing it.
I will take time and get to know my current equipment and setup my new scope when it arrives before deciding any further purchases.
*One thing I love is getting to know the night sky with what equipment I have now, and it is to me a wonderful challenge.

[SkyHiker]

I was a bit vague about the upper magnification limit. It is based on Dawes' law resolution r=lambda/D where lambda is the wavelength of light and r is the resolution of the human eye in radians, all in SI units. The resolution of the human eye is 60 arc seconds or pi*60/(3600*180)=291e-6 in SI. The resolution of the scope at 5000 Angstrom is 5000e-10/102e-3=49e-7. So when the magnification M=F/f times that number is larger than the human eye's resolution we are just adding noise. That would be at 291e-6/49e-7=60 times. As you can tell I like to do some early morning weekend mind gymnastics after my 2nd cup of coffee. Hopefully it all holds up.

That is a bit less than the rule of thumb number that I mentioned, D in mm, but close enough because there are some fudge factors. This explains why for planets you need a 14" SCT, only to find out that that you get that resolution maybe 2x per year because of atmospheric turbulence. On most evenings the resolution won't reach the Dawes limit for apertures above 8", but the amount of light captured is a different story. That's why Dobsonians larger than 25" are nice to have. At the same time, there are some small sized telescopes with great optics that produce spectacular images of larger objects because they are less affected by turbulence and mechanical tracking issues. Reflectors don't quite follow Dawes' limit because of the secondary obstruction, so a rule of thumb is to add 2" diameter compared to a refractor for the same resolution. That's the story pretty much in a nutshell.

[SkyHiker]

Getting back to the question, choose a scope with focal length of 660 mm or 1000 mm: we just calculated that the useful eyepiece focal lengths are from 15 mm to 49 mm, but who has a 49 mm eyepiece? Doing the same math for the 660 mm would lead to useful eyepiece focal lengths from about 9 mm to 30 mm, the upper limit of which is more commonly available, and it allows for a wider field of view. The downside is that the 660 mm will have more chromatic aberration but still within the limits. Ok I will stop now, HTH.

[pakarinen]

I placed an order with High Point Scientific for the Explore Scientific FirstLight 102mm Doublet Refractor with EXOS EQ Nano Mount.

Do post your impressions of that combo after you get it, especially how well the Nano handles the load.