Gonariu

I quietly solved M13 in stars with a C8 and a 20cm Newtonian.

@Louis D. Great, I didn't think a Dobson could compact in such a small space! I would like to ask you what kind of Newton the optic is and how much it all weighs.

I think a travel telescope must have these characteristics:
1) ultra-portable;
2) handyman tool.
3) that it can be mounted on a photographic tripod.
So I can see well an 80/400 refractor (the focal length is more or less that), then it depends on how much one wants to spend, if one wants to spend a lot on a pure apochromat, if he doesn't want to bleed his wallet too much an ED apochromat, if wants to save more an achromat. I lean towards the latter being a visualist; taking a nice travel to Namibia (for example) I don't start looking at the planets or the Moon, I look at them here in Sardinia, I would aim above all at deep - sky objects, in particular those that do not arise here.

I am spending the summer in Cagliari with my mother and I only have slices of sky with a little light pollution (not much, on the other hand Cagliari if it is as big as a London neighborhood is too much) so I mainly observe the Moon and the planets. The problem is that there is often wind this year either hot from the SE or cool from the NW, so the high resolution goes to hell. The other night I took advantage of the fact that there was no wind to pull out the Nexstar 8 SE and I went to bed at 3 in the morning: Jupiter fantastic, the Moon was phenomenal, Saturn did not mind, of the satellites you could only see Titan but with the Moon present was not night to see a few more. The Nexstar was a bit sensitive to turbulence but at 200X, as I said, the vision was beautiful. At 2 in the morning it occurs to me to quickly see the Moon with the Vixen 102 - M (achromatic 102/1000). At 167X it was the best magnification for image brightness, at 200X it was still fine, the image was contrasted and firmer than the Nexstar. In a few days I will have to go back to central Sardinia as from September 1st I have to go back to school in Nuoro: I will take advantage of the large terrace and the lower light pollution to see even some deep - sky objects, the weather remains warm or warm until for a good part of October, the past autumn I often looked at Mars through the telescope in a T-shirt; for now I am satisfied and do the last dives (due to the covid the mayor of Orotelli has imposed the mask when you leave, I call it "the gas mask": for heaven's sake !!!!).

Of course, the photograph of the mirror does not make us think well, is the instrument new or used? I have never bought anything from ebay, is there a possibility to make a return? Otherwise, if you keep it, I'm thinking that the mirror lighting needs to be redone. Here I leave the floor to the others.

Wow! The 6 ”has a 22% obstruction, great for planets, it's a universal tool! It would be interesting to know the prices.

Welcome to SGL Mainak from Sardinia! India must be beautiful to see !!!

Welcome to SGL Dave from Sardinia!

10 hours ago, Iem1 said:

Grazie Gonariu!

Sono fortunato ad essere in grado di raggiungere siti decenti con cielo scuro, quell'immagine è stata scattata nei Brecon Beacons (Galles, Regno Unito) che apparentemente è un 3-4 bortle. Va bene, dato che non ho filtri per l'inquinamento luminoso ..Anche se penso che la luna fosse a circa il 70% e abbastanza luminosa durante quella sessione di imaging. Devo ancora sperimentare l'AP senza la luna (nella regione di Sadr ho fatto circa la metà delle immagini prima che la luna sorgesse) 

sperando di poter uscire questa sera e riprovare senza alcun chiaro di luna, sia bello vedere la differenza.

I wish you good observations and beautiful photographs! If poltronite doesn't win me after dinner I see Jupiter with the Vixen 102M that I bought myself; I do not think it is a suitable day for either the planets or the deep-sky because there is a wind from the south that this morning made the sea agitated and the sky is certainly dull due to the suspended Sahara sand (apart from the light pollution of Cagliari).

7 hours ago, mikemarotta said:

Non faccio sempre disegni. Almeno inserirò note verbali, ma ogni tanto esco solo per vedere e divertirmi. Mi sdraierò su una chaise longue e userò un binocolo o semplicemente mi godrò il cielo a occhio nudo. 

You're right, after all astronomy is a hobby for us and not a job. I recognize that it is not always important to do in the sense of producing but also to look with a telescope or binoculars to make pure relaxing contemplative observations!
I also offer you my best regards and happy holidays.

Agostino Zoroddu alias Gonariu.

I state that I do not know astrophotography, I like your photographs of M31 very much! Apparently where you live the white nights are over!

I draw a drawing of what I observe in a notebook. In addition, I add the date and time, the instrument used and some other notes such as "veiled sky", "strong wind" and so on. I never figured out how to evaluate seeing and honestly never tried…. I do this job for my observations of the Sun and Mars, with Jupiter I am only now able to see more (I thought that in a telescope one could see who knows what ...) but also the last time I looked at it with a achromatic Vixen 102M a few days ago, out of laziness I did not make any drawings. As a math and physics teacher I recycle my observations of the Sun from when I was a boy to show them to my students who are interested (and getting kids interested in what is taught today is not easy!).

I observe the Sun almost every day with my achromatic 80/400 and with a glass solar filter at full aperture, this summer and when I am in Cagliari with my mother is my main astronomical activity. Unfortunately in Cagliari I have slices of the sky and you don't see much (in addition to light pollution which I don't think is so disastrous). In Orotelli I also have a nice terrace but ... .... to go to the beach you have to do one way 60/70 km while in Cagliari I go there by city bus (by car to the beach of Cagliari, the Poetto, I would not find room in the morning for park, but travel well: I always sit, there is air conditioning and in the meantime I read a few books). The problem is that when you go out in Orotelli during the winter you have to freeze your ears and dentures (compared to Cagliari there are about 5 ° less than in Cagliari, more or less the temperature than it would in London), so I tend to stay warm ... ..
The Skywatcher mak 180/2800 must be divine on the Moon, planets and double stars, I've always heard a lot of good about it (I've never tried it), I discarded it because I prefer a more universal instrument and because it is a little heavy. I have an EQ5, certainly for visual use it would still hold it, but….

Welcome Arty to SGL! You have beautiful tools!

On 4/8/2021 at 17:34, vlnikolic said:

vlaiv, grazie per una risposta dettagliata. Penso di aver imparato molto nel frattempo (molto rispetto alla mia posizione di partenza eheh)

stavo pensando ad un'altra possibilità:

SkyWatcher Startravel 120T AZ3

I have a Ziel 120/600 achromatic refractor (the Ziel GEM 60) that I bought in 2011 and that I keep in Cagliari at my mother's house (I bought it so as not to be starved of astronomical observations when I go there for the holidays) . I use it to see the Moon at 150X (with a 4mm Vixen Lanthanum eyepiece) and last year also to see Mars at 200X - 3000X (high magnification for a short focus achromat, personally I find it better not to exceed 200X ), I will tell you that the Moon can be seen well despite the chromatism (the lunar edge has a beautiful blue halo ....) and on Mars last year, mounting the telescope on an equatorial EQ5 and tracking by hand I made some beautiful observations . I put my drawings that I made of Mars in an Italian forum of which this is the link: https://astro.forumfree.it/, to see them just click when a short blue refractor appears on the variable screen. in Italian “Osservando Marte con un 120/600” ( = "Observing Mars with a 120/600" in english). In these drawings I write in Italian and often in italics, if you need to ask me something about it no problem. I also bought the semi-opaque filter from Baader Planetarium which reduces chromatic aberration (but does not cancel it) looking at the Moon and Venus, but on the Moon I preferred to remove it because I liked a brighter image. I have been wondering for some time if the fringe killer filter or the contrast booster is better than the half-op. 

Hello and welcome to SGL from Sardinia! Beautiful images, very good !!!

Hello and welcome to SGL from Sardinia! A 10X50 binoculars and a 200/1000 Newtonian are a winning combination, binoculars are complementary to a telescope!

To start with, there are three telescopes that are fine. I see poorly the red dot finder to use the telescope to see the landscape as the red dot is visible only at night and not during the day, here you need a classic finder. Keep the following things in mind:
1) I have seen from the links you put that propose these telescopes at exaggerated magnifications using a Barlow 3X, in particular 675X for the 90/900 refractor and 487.5X for the Newton 130/650 that are absolutely useless. The resolving power of a telescope is given by the formula P = =120/D (the formula comes from wave optics), with D diameter of the objective in mm and P in seconds of arc. For example, the 90/900 will therefore have a resolving power of 1.3 "which are the closest details that the optics will be able to resolve, a double star whose components are 0.8" apart, the 90/900 will not be able to separate it whatever magnification you put and the same is for two details of the lunar surface; therefore to see more you have to increase the diameter of the objective (lens or mirror). The maximum magnification that a telescope can exploit is 20 - 25 times the diameter of the objective in cm, therefore 180X - 225X in the case of the 90/900;
2) the refractor 102/660 is beautiful for landscapes and deep sky objects, it is less or less good for the observation of the Moon and planets at high resolution (and therefore at high magnification) due to the fact that the chromatic aberration is not well corrected as the focal length is too short. To be negligible the chromatism the focal length f must satisfy the relation f> = D^2 (with f and D in cm) otherwise it makes itself felt with a decrease in resolution. Here at least in part it can be remedied with a light yellow W8 filter or some other special filter (contrast booster, fringe killer, the Baader semi-opener). Another problem could be spherical aberration as it is less easy to work well with lenses with such a short focal length. Here I can tell you that I have two short focus achromatic refractors, a 70/400 and an 80/400. The first on the planets is like this, on Jupiter you just distinguish the two main bands at 100X, the second is much better, on Mars last year I distinguished Syrtis Maior and the south polar cap at 160X - 200X, on the Moon it did not mind and the vision was more contrasted with the W8 filter or the semi-opaque one of the Baader Planetarium. The problem is that these optics are all Chinese and do not control them in a maniacal way as Astrophysics does, so the successful model or that can happen.
3) Make sure that for the Newton 130/650 that the mirror is really parabolic as it says in the link, usually for these entry - level instruments they put a spherical mirror that to work well must have at least a certain focal length, 650 mm are few. In an Italian forum one said that he had taken a Newton 130/650 (I think from Skywatcher) that beyond 100X could not go due to the non-negligible spherical aberration due to the spherical primary mirror. So if you find out that the mirror is spherical, forget it. Also consider that a Newtonian is not ideal for panoramas due to the blind spot due to the secondary.

As soon as I can I buy it. I look at the Sun every day with my achromatic 80/400 using a glass solar filter at full aperture, also making the drawing. In the past school year I proposed to the school where I teach, the ex magistrali of Nuoro, the observation of the Sun for interested students, discarding the nocturnal observation to involve anyone who wanted it (half of our students come from the villages). I think I will buy this book too, if I consider it appropriate I will propose it to my school for purchase.

Welcome! What is the focal length of your achromatic 100 mm?

Welcome! Nice tool yours!

I will tell you that I cannot imagine a night without night (ie without darkness), here in Sardinia we are at an average latitude of 40º. Can you at least observe the Moon and planets?

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@Maxim Usedv. Beautiful review, a great comet hunter, William Bradfield, used an achromat of this type. Very nice photography of Stonehenge, if one goes to the UK to see Stonehenge is a must!

Welcome to SGL. A few years ago the school where I teach in Nuoro (in central Sardinia) also bought a Nexstar 6 SE, it's a nice telescope!

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Hi Kayle, I think a 76mm Newtonian to start is fine. When I was 16 in 1983 I bought a 60mm 700mm focal length telescope with lens (achromatic refractor 60/700). Assuming that the telescope optics are collimated, you have to adjust the finder with screws that you will easily notice. In the finder you see a cross and when it is collimated what you see in the center of the cross you also see it in the center of the telescope. If this is not the case what you put in the center of the finder you do not see it at the telescope, so first point with the finder at a distant detail (for example a lamp on a street lamp), by attempting you put it in the center of the telescope (which must have an eyepiece at low magnification, I used to put 35X) and adjust the screws that I told you before, the thing must be done by trial and error. This operation must be done during the day. Once you have done this you can see what you want, within the telescope's potential of course.