What is Reddit's opinion of SVBONY SV197 Collimating Cheshire Eyepiece, 1.25 Inch Collimation Eyepiece, for Newtonian Reflector Telescope?

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Unfortunately without a picture through a collimation cap or a cheshire, or something that forces the camera to be in the exact center of the focuser, it's impossible to say whether this is fully collimated or not.

I recommend getting a cheshire. This will help you fully collimate your scope.

The peephole in the center of the cheshire ensures all alignment is referenced from the center of the focuser tube. You will be able to center the secondary under the focuser, and using the crosshairs, adjust the secondary tilt such that the center spot of the primary is centered under the the crosshairs. When that's done, you can adjust the primary to ensure the center spot matches the reflecting ring of the cheshire.

Without such a tool, you're basically just guessing and relying 100% on eyeballing the collimation, which in my experience, is rarely accurate.

This is about as basic as it gets...Prime day sale too.

When you say "fancy gear" do you know what they had? There's all kinds of stuff out there...but you can get more than adequate collimation at f/6 with just a cheshire.

Definitely get a cheshire. It's more useful than a laser collimator at doing a full collimation procedure on the scope. A laser collimator is more convenient when doing simple tweaks afterwords.

Generally when you have your secondary mirror collimated, you don't need to touch it much. Just minor tilt adjustments.

You can get either the Svbony 1.25" cheshire: https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M

Or go for a more expensive option like an Astrosystems Lightpipe or Cats Eye Collimation TeleCat.

Ideally you want your cheshire to allow you to align the edges of the secondary mirror to the inner edge of the cheshire. This will determine correct secondary placement under the focuser.

This is a good one to get:

https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M/

Unlike most of the basic ones, this one can be inserted all the way down into the focuser, which makes it more flexible in getting the right position for aligning the secondary and making sure you can see the whole primary mirror.

I think you have a 6" F/8 scope, so in that case, I recommend this specific one:

https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M

Unlike most basic cheshires, this can be fully inserted into the focuser. This has a couple of advantages:

1. It lets you adjust the position so that you can match the outline of the tube to the outline of the edge of the secondary mirror to better determine accurate positioning of the secondary mirror. It also lets you adjust it so that you can see the whole primary mirror.

2. If you insert it all the way, you can ensure it sits flat against the focuser rim, which can aid in alignment when doing the actual tilt adjustment of the secondary and primary.

Your collimation is reasonably close, and given the scope is F/8, collimation tolerance is quite high so I'd say you're close enough.

That being said, if you want to be precise about it, a collimation cap is not sufficient for complete collimation of a scope. It's better than eyeballing down the focuser without one, but if you want thorough collimation, you'll want a cheshire: https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M

The procedure is this:

Step 1: Center the secondary mirror under the focuser

Insert the cheshire into the focuser all the way and rack the focuser all the way in. Look through the cheshire and look at how centered the edges of the secondary mirror look in the view. Ignore the reflection of the primary mirror, just look at the physical edges of the secondary mirror. It helps to put a white sheet of paper behind the secondary so that you can see the outline of the secondary more easily.

If it looks centered, proceed to step 2. If it looks off-center, then appropriately loosen/tighten the FOUR bolts holding the secondary to the vane to move it laterally (closer to the primary mirror or farther from the primary mirror) until it's centered under the focuser.

If it doesn't look round, then there may be a rotational error, so you'll want to slightly loosen the three collimation screws, and rotate it slightly until it looks round. Ideally it should be fully concentric with the edge of the cheshire sight tube.

Once this step is done, it rarely every has to be performed again.

Step 2: Adjust the secondary mirror tilt

With the secondary mirror centered under the focuser and concentric with it, the next step is to aim the secondary at the primary. The way you do this is you adjust the three collimation screws of the secondary mirror until the center spot of the primary mirror appears to move underneath the crosshairs of the cheshire. You can see the center spot on your primary mirror when look through the cheshire. That is your target. As you adjust the secondary mirror's tilt, the center spot will appear to move, and you're goal is to move it under the crosshairs of the cheshire. When that is done, your secondary mirror is fully collimated.

Step 3: Adjust the primary mirror tilt

The last step is to adjust the primary mirror. The Cheshire has an angled reflecting ring on it. Turn it until it catches a light source and appears as bright as possible when looking through the cheshire. The center spot of the primary mirror should appear as a silhouette against it.

Adjust the primary mirror collimation until this bright reflecting ring appears to move behind the center spot of the primary. The donut of the center spot should be centered directly over the peephole in the cheshire.

At this point, the telescope is fully collimated.

Alright, here's my best estimate of your collimation from the image:

https://i.imgur.com/4Ezyrfc.jpg

As above, the large green circle is your focuser, which is the frame of reference for everything. The smaller green circle is the ideal location of the outline of the secondary mirror, and the orange circle is the actual outline of the secondary (as best as I could estimate).

While you have the center donut centered on the reflective ring of the collimation cap, the secondary mirror position and alignment are off. This is the downside to a collimation cap - you don't have crosshairs to help you align the secondary like a cheshire would allow.

Before doing any further collimation, I strongly recommend getting a cheshire sight tube with crosshairs in it. This is the best entry-level one, with the next step up being an appropriate Astrosystems Lightpipe, followed by a Cat's Eye Collimation TeleCat.

When you have that tool, collimation will need to be done in three steps:

1. Center the secondary mirror in the focuser tube as best you can. The adjustable Cat's Eye TeleCat makes that dead simple, but you can eyeball that with other cheshires. I recommend blocking the view of the primary with a white sheet of paper so as not to distract yourself with anything else. your goal is to simply to make it so the outline of the secondary mirror looks as round and concentric with the bottom of the focuser tube (or the bottom of the cheshire - whichever you can see), as possible.

2. Next you will want to remove that sheet of paper blocking your view of the primary if you put on in, and then using the crosshairs of the cheshire, adjust the tilt of the secondary collimation until the center spot of the primary mirror appears to move behind the crosshairs. You want the crosshairs aimed at that center spot.

3. One that's done, then you adjust the primary mirror tilt until the bright reflecting ring in the cheshire appears to move behind the center spot of the primary mirror. At that point you should see the crosshairs still aimed at the center spot, the center spot centered on the reflecting ring of the cheshire, and all three mirror clips of the primary mirror should be visible with equal spacing all around it.

You may have to repeat steps 1 through 3 after an initial collimation pass, but the adjustments will be a lot more subtle.

But I do strongly recommend a cheshire. Collimating without one is much harder to get right.

The accessories it comes with are WAY better than the ones that come with other 8" dobs. However, while they are definitely enough to get you started, eventually you'll want to consider additions/upgrades.

1. The laser collimator is handy, but a laser collimator by itself cannot fully collimate a reflector. You may want to consider a cheshire collimator like an Astrosystems Light Pipe or just a basic one like this to help ensure the secondary mirror is properly centered under the focuser. Once the secondary mirror is centered under the focuser and concentric with it, the laser collimator is a great tool for quickly spot checking collimation and making minor tweaks.

2. The 9mm Plossl the scope comes with is a great conservative planetary focal length, giving 133x magnification. However, the nature of a Plossl design is that the eye relief is short, and the field of view is narrow. You may find it's hard to look through, and doesn't give you a lot of drift time before you have to re-center the planet. You may want to consider upgrading this eyepiece to a more comfortable widefield like an 8mm Astro-Tech Paradigm / Agena StarGuider Dual ED, or 9mm Celestron X-Cel LX. Or go more into a premium eyepiece from Tele Vue, Explore Scientific, Nikon, Pentax, or Baader. Lots of options in the 8-10mm focal length range, so depending on your budget for upgrades, we could make some recommendations.

3. The 30mm GSO SuperView you get with the telescope is WAY better than the low power eyepieces you typically get from other scopes. You can definitely live with this eyepiece for a while. The views are generally excellent through it, but the only defect you might notice after a while is the edges of the field of view won't necessarily show clean star images. The stars may look a little distorted out towards the edges (but they'll be wonderfully sharp in the center). If you were picky enough, you could fix this buy upgrading to a 30mm APM Ultra Flat Field (or 30mm Meade UHD or 30mm Celestron Ultima Edge - all the same eyepiece). Or if you wanted to spend big bucks on an ultra-wide field, you could get the 30mm Explore Scientific 82 or the 31mm Tele Vue Nagler. But these are almost as much as the scope cost!

But two eyepieces won't be enough to cover all your needs, so you would want to consider some additional ones:

1. Definitely get a 12mm wide angle eyepiece at some point. This would produce a 2mm exit pupil in an F/6 scope, giving you a great balance of view brightness and magnification for general purpose deep sky observing. 12mm may be too close in focal length to a 10mm eyepiece if you ended up going that route, so you could get a 13mm or 14mm eyepiece instead. But I would definitely try to aim for a 12mm if you can.

2. Take whatever conservative planetary eyepiece you got (be it 8mm, 9mm, or 10mm), and then add 3-4 more focal lengths in 50x magnification jumps. In an 8" F/6 scopes, a good spread might be 8mm (150x), 6mm (200x), 5mm (240x), and 4mm (300x). These will be useful for doing planetary observing, and the reason for the ~40-60x jumps in magnification is to let you choose an eyepiece that is appropriate for the night's observing conditions. Some nights will allow for high power, some nights won't. Note that you don't have to stick to exactly those focal lengths. Another spread might be 9mm, 7mm, 5mm, 4mm or even 9mm, 6.5mm, and 4.5mm. Bigger jumps, but still good.

3. In general, a complete spread of eyepieces might be something roughly like this: ~30mm, ~17mm, ~12mm, ~8mm, ~6mm, ~5mm, ~4mm.

Also consider getting one or two good quality 2" nebula filters for enhancing emission nebulae. A good quality UHC/narrowband would be a general purpose emission nebula filter, and you could also add an O-III filter to further enhance contrast of certain targets. Note that good ones are expensive - $240-280 - but they are worth it over cheaper filters. Tele Vue, Astronomik, and Lumicon make the best filters.

Another thing to consider adding is a Telrad or Rigel Quikfinder. These are reticle sights that just project a virtual red reticle on the sky to make rough aiming the scope easy. A reticle sight in conjunction with the RACI finder the scope comes with is a powerful combination for finding objects.

And lastly, get a nice foam hard case for storing all your eyepieces and gear safely. Something like the Harborfreight Apache cases or similar would be good. Pelican makes very nice cases, but they're expensive. I also recommend keeping some Dry & Dry desiccant packs in the case when it's closed as this will keep the contents dry and stop optical fungus from attacking the eyepieces.

I assume your dob has a center spotted primary. If it doesn't, then you will need to add one for any collimation tool to be useful.

I also recommend getting a cheshire. It will allow for more complete collimation of the scope.

Here's an entry-level one I recommend:

https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M

The smooth barrel lets you position it insert it into the focuser at any point to help you align your secondary mirror.

The first step is adjust the secondary mirror's forward/back position, and rotation, so that it's concentric with the inner bottom edge of the cheshire.

The second step is to tilt the secondary so that the center spot of the primary mirror appears to move underneath the crosshairs of the cheshire.

The third step is to tilt the primary so that the reflection of the bright reflecting ring of the cheshire appears to move behind the reflection of the center spot on the primary.

Once those three steps are performed, your scope will be well collimated. You can tweak and fine-tune collimation by doing a high magnification collimation test against Polaris at a magnification of 35x per inch of aperture.

After that, I recommend you tweak the collimation of your laser collimator (it should have adjustment screws to do this). And then you can use the laser collimator to do quick "maintenance" collimation. Once the secondary mirror has been positioned under the focuser, it rarely needs adjustment later. Only minor tilt adjustments are necessary, and those are fine to do with a laser collimator as long as you know the laser is accurate.

That's basically my procedure. I centered the secondary under the focuser once using my adjustable cheshire, and then when I'm out in the field, I'll use a laser to do a 30 second collimation tweak of the secondary mirror tilt, and primary mirror tilt. I do that before every observing session. Sometimes a small adjustment is needed, other times no adjustment is needed.

I have a 12" f/5 dobsonian (Meade Lightbridge) and found that a 1.25" cheshire did not let me see the whole secondary or primary adequately. But I have an annoying kind of cheshire that doesn't insert all the way into the focuser.

This Svbony collimator lets you change how far into the focuser you insert it so that you can potentially set it to let you see the secondary more easily:

But ideally you'd want a 2" cheshire for F/4+ scopes like an AstroSystems Light Pipe: https://www.eyepiecesetc.com/ASTROSYSTEMS_LIGHT_PIPE_2_f_4_2_p/11401006.htm, or even better, a TeleCat XL: https://www.catseyecollimation.com/sighttubes.html, which has an adjustable draw tube and focal ratio guide to help you really nail the secondary mirror alignment.

A cheshire is a more comprehensive collimation tool, but a laser is very convenient for maintaining collimation (especially when it's dark). I use both tools.

As far as the secondary being difficult to adjust, I have the same problem with my Lightbridge. Despite having thumb screws, the secondary is an incredibly annoying thing to align for some reason. You basically have to make very, very small adjustments. If you want to tighten one screw, you have to back off the other screws by an equal amount. It feels like it wants to make the laser dance all over the place. There's no real solution that I know of.

> Is there a reason they are not as mentioned on the sub, as other models/brands? Is this telescope a good first telescope?

It's a fine scope. I think this sub has more North America visitors so there's probably a bias towards recommendations for gear in North America than Europe.

That said, before the pandemic made everything crazy, a full size 150mm dob like the Sky-Watcher Classic 150p was cheaper, and the size + F/8 focal ratio of a full size dob is preferable to an F/5 table-top in a lot of ways (but also has some drawbacks).

The only issue I have with the scope you linked to is the secondary mirror is oversized - likely to allow one to reach focus natively with a DSLR, but IMO doing DSLR AP on a dob is pointless. The secondary mirror should have been smaller so that it would block less light, and more importantly, have better contrast from less diffraction effects.

> Are the accessories in the package adequate for starters? What else should I get?

Eyepieces aside (which I'll address below), I'd recommend just a couple of things to start:

1. A nice hard case with foam to keep your accessories and eyepieces safe.
2. A red light is handy if you travel out to dark skies. Observing from within the city should be bright enough to see what you're doing without a light (but that means you'll be limited to the Moon and planets for observing).
3. A collimation tool of some kind. This Svbony cheshire is a good choice. It lets you vary its position within the focuser to more easily see the whole secondary mirror. Helps with alignment.

I don't know if the Bresser has a center-spotted mirror, but you'd want to center spot it yourself so that the cheshire will be more useful.

The other accessories the scope comes with aren't great. The Moon filter is pointless and the two eyepieces are cheap and won't put up good views in an F/5 scope. The red dot sight is iffy, but it should be enough for rough pointing.

> What eyepieces should I start looking for?

It depends on your budget. This scope's oversized secondary mirror and 2" focuser allows you to use 2" wide angle eyepieces for low power views, but these will be a lot more expensive than a typical 1.25" 32mm Plossl.

Do you have a budget in mind in total for all eyepieces (or at least a budget per eyepiece?)

It's likely very roughly collimated, but you'll definitely want to perform a collimation check yourself to be sure. The secondary is most likely to be collimated with respect to the focuser, so you'll just have to ensure it is aimed at the primary mirror, and the primary is also collimated.

Did your AD8 come with a laser collimator? I know they were included in the package for a while, but they might have stopped including them.

If you don't have a collimation tool, I recommend getting a cheshire instead of a laser. A basic one is this Svbony: https://www.amazon.com/SVBONY-Collimating-Collimation-Newtonian-Reflector/dp/B092ZW9X9M

A better quality one is a 2" AstroSystems Light Pipe: https://www.eyepiecesetc.com/ASTROSYSTEMS_LIGHT_PIPE_2_f_4_2_p/11401006.htm

A cheshire with crosshairs in it is technically all you need. You don't need a laser. This Svbony one is the best entry-level option.