Refractor or Mak??

[BigD]

A little advice please.

I thought I had it all figured out but ......... now that I see them up close and in-person and start comparing the deals, I am having trouble figuring out which is better for my situation?

Situation: 60% land viewing of ships 1-5 miles away 40% moon/planets (ideally see the red spot on Jupiter and some detail of Saturn rings).

Right now I'm trying to decide between:

127mm or 5" Mak with a 1500mm focal length

150mm or 6" short tube Refractor with 750mm focal length

120mm or 4.7" long tube Refractor with a 1000mm focal length


Any comments or advice?

[Maksutov]

Mak


-Mak

[SarahMc]

A little advice please.

Situation: 60% land viewing of ships 1-5 miles away 40% moon/planets (ideally see the red spot on Jupiter and some detail of Saturn rings).

Right now I'm trying to decide between:

127mm or 5" Mak with a 1500mm focal length

Excellent for both situations.

6" short tube Refractor with 750mm focal length

The wide field won't do so well on planetary detail, or for higher power detail in your terrestrial views. Nice for extended astronomical objects, and wide field terrestrial views at lower powers.

4.7" long tube Refractor with a 1000mm focal length

Would do well for your purposes, but will have chromatic aberation on the bright planets (if it's an achromat) where the Mak would not. It's also much larger than the mak, making it less portable. I agree with Maksutov; his reply wasn't just because of his name If you get the mak, buy (or make) a dew shield for it.

[aurora]

If portability is not a concern (doesn't sound like it), I would go against the other advice and suggest the refractor.

I find a refractor better in the daytime than a Mak, and since you said 60% of the use will be daylight...

Better yet, is there a store or an astronomy club nearby where you can try them out for yourself?

[A Thousand Pardons]

Would do well for your purposes, but will have chromatic aberation on the bright planets (if it's an achromat)

Did you mean, "if it's not an achromat"?

[SarahMc]

Would do well for your purposes, but will have chromatic aberation on the bright planets (if it's an achromat)

Did you mean, "if it's not an achromat"?

Nope. If it was an apochromat, it wouldn't have chromatic aberation - or at worst a very small amount, depending on the manufacturer, glass used, etc. Achromats (at least the vast majority of them) have quite a bit of chromatic aberation, especially those at the lower end of the price scale.

[rleyland]

Would do well for your purposes, but will have chromatic aberation on the bright planets (if it's an achromat)

Did you mean, "if it's not an achromat"?

hmm, maybe, but more likely not:

Refractors come in three basic varieties:

- Un-corrected - basically a single objective (front) lens

- Achromat - two lenses closely coupled that will correct some color aberrations

- Apochromat - three lenses which will correct almost all color aberrations

On really bright objects like planets, you need an apochromat to avoid violet fringes. For daytime use an apochromat would be overkill.

An achromat can be used for planets but will have color fringing, and some people don't find the color objectionable, or with filters to eliminate some of the problems ( a -violet filter will help, or a "chromacorr" ). For daytime use it should be fine.

An uncorrected (dime store) telescope would be truly awful for planets! And not that great in the daytime either... think "spyglass"

My recommendation: the Mak is going to be the most portable and give you the most bang for your buck!

And lest anyone think I'm being biased here... I have a nice achromat telescope that is great for widefield views, but awful on planets. I have a 5" Mak that is wonderful on planets, and someday I might save up enough to buy a nice apochromat, but probably not as my 17" Dob gets more use than any of the other telescopes I own!


cheers,
Robbo

[A Thousand Pardons]

Oops, miss read that. Sorry.

[frogesque]

I bow to the superior knowledge of those who have commented on the astro side of the equation but for terrestial use (especially coastal) there will be times when you're going to get caught out with rain or salt spray. Easy to clean a lens, not so reflecting mirror surfaces. Also make sure critical fittings are marine friendly.

[Maksutov]

I bow to the superior knowledge of those who have commented on the astro side of the equation but for terrestial use (especially coastal) there will be times when you're going to get caught out with rain or salt spray. Easy to clean a lens, not so reflecting mirror surfaces. Also make sure critical fittings are marine friendly.

Those "open tube" environmental considerations are not applicable to a Mak. Maks are sealed by the meniscus corrector shell on one end and the eyepiece/mounting assembly (like a refractor) on the other end.

As with any telescope, when there is no eyepiece in place, the eyepiece mount should be capped or otherwise sealed off.

[frogesque]

Thanks for the info Maksutov I guess the Maks have it then

[BigD]

I did get to see a 90mm Mak and an 80 mm Refractor up close during the day with a 25mm eyepiece and when we changed to a 10mm eyepiece I thought I noticed the image was darker like putting on sunglasses with the Mak but did not notice it with the refractor.

Is this my imagination? or a passing wispy cloud?

===============================================

Also does the extra focal length difference help the Mak, comparing say:

127mm Mak with a 1500mm focal length

or

127mm Refractor with a 1200mm focal length


Is the Mak still better?

===============================================

And one last question:

Celestron 130mm Mak with a 2000mm focal length

or

Skywatcher 127mm Mak with a 1500mm focal length


Which is better for my situation?



PS - My luck they are probably made in the same Synta factory in China by the same guy ...

[Wolverine]

I did get to see a 90mm Mak and an 80 mm Refractor up close during the day with a 25mm eyepiece and when we changed to a 10mm eyepiece I thought I noticed the image was darker like putting on sunglasses with the Mak but did not notice it with the refractor.

Is this my imagination? or a passing wispy cloud?

That's inherent with increased magnification, in any telescope. The more an object is magnified, the dimmer it becomes in the field of view. For example, if you double the magnification while observing a given object, whatever you're viewing becomes four times as dim in the eyepiece, 3x the magnification results in an image 9x more dim, and so on. This is why the best views are obtained via lower magnifications, and why aperture is more important than magnification, since telescopes that can gather more light can offer higher usable magnifications.

[JustAGuy]

60% viewing land? I'd say go with the shortest FL Mak you can find. My 127mm Mak is great for dual purpose, but the only thing that bugs me about it is the limited field of view the 1900mm FL causes.

A much faster FL would be a significant improvement to this scope, IMHO. Something like an f/8 would still allow you to jack up the mag with a barlow, while remaining useful for low power observing (my FOV is about 1.5 degrees with a 40mm eyepiece).

[aurora]

I did get to see a 90mm Mak and an 80 mm Refractor up close during the day with a 25mm eyepiece and when we changed to a 10mm eyepiece I thought I noticed the image was darker like putting on sunglasses with the Mak but did not notice it with the refractor.

there are two possibilities I can think of. The magnification was already mentioned, since the Mak probably had a longer focal length, it would result in a higher magnification with the same eyepiece. that could explain what you saw.

Another point is that a Mak (like a newt or a SCT, and unlike a refractor) has a central obstruction. In the daytime, with certain eyepieces, you may be able to actually see the obstruction, the secondary mirror. At night, you won't be able to see it at all.

This may or may not bother you, obviously based on the responses in this thread from people who use Maks in daylight it wasn't an issue for them.

[BigD]

60% viewing land? I'd say go with the shortest FL Mak you can find. My 127mm Mak is great for dual purpose, but the only thing that bugs me about it is the limited field of view the 1900mm FL causes.

So in that case, I would be better off with the 127mm Mak from Skywatcher rather than the 130mm from Celestron because its FL is only 1500 instead of 2000 with the 130mm Celestron.

Is that right?

What is a reasonable power for daytime use that you get out of a 127mm Mak with a 1500mm FL?

[JustAGuy]

60% viewing land? I'd say go with the shortest FL Mak you can find. My 127mm Mak is great for dual purpose, but the only thing that bugs me about it is the limited field of view the 1900mm FL causes.

So in that case, I would be better off with the 127mm Mak from Skywatcher rather than the 130mm from Celestron because its FL is only 1500 instead of 2000 with the 130mm Celestron.

Is that right?

What is a reasonable power for daytime use that you get out of a 127mm Mak with a 1500mm FL?

Most of my daytime viewing is limited to pretty low powers, 50-~150x. Much higher and you have to limit yourself to mornings, before the heat distortion becomes an issue (although some cold afternoons I've been able to push 250-300).

As for the two scopes, I can't comment too much as I don't know a lot about the pros and cons of those manufacturers. Strictly on a focal length basis, I'd go with the Skywatcher (f/12 vs f/15). A 40mm eyepiece would give you lower resolution in the Skywatcher (38x vs 50x), but wider field of view (~1.3 deg vs ~1.0 deg), which can be pretty important in terrestial viewing.